940 results on '"Double sampling"'
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202. Construct, generalization and luck in danish oral examinations in upper secondary school
- Author
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Julie Marie Isager
- Subjects
Secondary level ,lcsh:LC8-6691 ,lcsh:Special aspects of education ,assessment ,Denmark ,mundtlig eksamen, assessment, konstrukt, gymnasiet, Danmark ,Score interpretation ,Education ,Construct ,Double sampling ,Danmark ,mundtlig eksamen ,Oral examination ,gymnasiet ,Sociology ,Oral exam ,Upper secondary school ,Humanities ,konstrukt - Abstract
Danske gymnasieelever bliver – ligesom norske – eksamineret ved mundtlig præsen-tation og samtale om et udtrukket emne af deres lærer og en censor fra et andet gymnasium. Disse eksaminer undersøges ikke systematisk, og der forskes ikke i dem. Det samlede eksamensresultat er high-stakes og får konsekvenser for elevens fremtidige uddannelsesmuligheder. Artiklen undersøger centrale danske styredokumenter, der regulerer mundtlige danske eksaminer i gymnasiet ved at lægge et teoretisk blik hentet fra international anerkendt assessmentteori: Hvad intenderer eksamen at måle? Assess¬mentteoretiske begreber defineret af Standards for Educational and Psychological testing og Michael T. Kanes argumentationsbaserede tilgang til validitet bruges til at søge efter et konstrukt og slutninger i eksamenssystemet. Data er lovdokumententer samt læreplan og vejledning i historiefaget som eksempel i det almene gymnasium med et almendannende og studieforberedende formål. Dermed er artiklen et tillæg til Acta Didactica Norges temanummer vol. 12 nr. 4 om Test og eksamen i Sverige og Norge. Studiet finder, at konstruktet er vanskeligt at identificere. Antagelser om mundtlige eksaminer er ikke ekspliciterede i dokumenterne, og slutninger må analyseres frem. Eleven eksamineres i et dobbelt udtræk- eller samplingssystem: Eksamensfaget udtrækkes og emnet inden for disciplinen udtrækkes. Der etableres dermed en antagelse om vidtgående generaliseringsmulighed af testresultatet på tværs af fag. Det diskuteres om assessmentteori egner sig til diskussion af traditionsrige danske mundtlige eksaminer. Nøkkelord: mundtlig eksamen, assessment, konstrukt, gymnasiet, Danmark Construct, Generalization and Luck in Danish Oral Examinations in Upper Secondary School AbstractDanish and Norwegian upper secondary school students are assessed on their presen-tation and discussion of a sampled topic by their teacher (the examiner) and a teacher from another school (external examiner). These oral exams are not investigated systematically even though they are high stakes tests with considerable consequences for the students’ potential choice of further education. The article investigates the construct of the oral exam: What are oral exams intended to assess? Data are key law documents, the curriculum and the instructions given for the subject of History as an example. The documents are read with assessment theory as defined in the Standards for Educational and Psychological Testing and Michael T. Kane’s argument-based approach to validity. The study finds that the construct is difficult to identify. No explicit arguments or inferences are found in the documents read, and inferences must be interpreted between the lines. Each student is assessed in a double sampling system: The subject is sampled, and the theme of the exam is sampled within the subject. The article shows a system built with inferences of extensive generalization from one score interpretation to potential other performances across the curricula. It is discussed whether assessment theory is adequate for the Danish educational traditions. Keywords: oral exam, assessment, construct, upper secondary school, Denmark
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- 2020
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203. Double Sampling Using Poisson Applications
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John J. Heldt
- Subjects
symbols.namesake ,Double sampling ,symbols ,Applied mathematics ,Poisson distribution ,Mathematics - Published
- 2020
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204. An Improved Regression Type Estimator of Population Mean with Two Auxiliary Variables in Stratified Double Sampling
- Author
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Amanpreet Kaur and Lovleen Kumar Grover
- Subjects
Statistics and Probability ,Auxiliary variables ,Mean squared error ,Double sampling ,Population mean ,Statistics ,Estimator ,Survey sampling ,Type (model theory) ,Regression ,Mathematics - Abstract
Shabbir (Commun Stat Theory Methods 47(1):92–101, 2018) suggested a new difference type estimator of finite population mean in stratified double sampling using the ranks of two auxiliary variables as additional information. In this paper, on applying Searls’s (J Am Stat Assoc 59:1225–1226, 1964) approach to Shabbir’s (2018) estimator, we propose an improved estimator of population mean. The expressions of bias and mean square error of the proposed estimator have been obtained, up to first order of approximation. Theoretical and numerical comparisons of the mean square error of the proposed estimator with that of various existing estimators have been made. It is observed that proposed estimator always performs better than Shabbir’s (2018) estimator and also better than most of the other various existing estimators in the literature of survey sampling.
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- 2020
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205. The Performance Study of Double Sampling Coefficient of Variation Control Charts
- Author
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Chau-Chen Torng, Hao-Ren Jhong, and Pei-Hsi Lee
- Subjects
Process quality ,Double sampling ,Chart ,Coefficient of variation ,Statistics ,Control chart ,Step detection ,Statistical process control ,Reliability (statistics) ,Mathematics - Abstract
Statistical Process Control (SPC) is widely used in practice, and the control chart is a main tool in SPC. The control chart monitors process quality and detects process variations in real time to reduce the defective products. Regulatory maps are used in clinical trials and agronomic industries, and the mean and variance are not constants, and the coefficient of variation is an indicator of the reliability of chemical tests. However, the coefficient of variation control chart (CV Chart) monitors the coefficient of variation, and the ability to detect small shift sizes is not good. This study uses a double sampling plan combined with a coefficient of variation control chart (DS CV chart) to improve the performance of CV Chart. A design model of DS CV chart is also created to optimize its parameters. The results of the study show that the good performance of DS CV chart in small shift detection.
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- 2020
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206. A Design and Evaluation of Coefficient of Variation Control Chart
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Chau-Chen Torng and Hao-Ren Jhong
- Subjects
Process quality ,021103 operations research ,Coefficient of variation ,0211 other engineering and technologies ,02 engineering and technology ,Statistical process control ,Double sampling ,Chart ,Statistics ,Step detection ,Control chart ,021108 energy ,Reliability (statistics) ,Mathematics - Abstract
Statistical Process Control (SPC) is widely used in practice, and the control chart is a main tool in SPC. The control chart monitors process quality and detects process variations in real time to reduce the defective products. Regulatory maps are used in clinical trials and agronomic industries, and the mean and variance are not constants, and the coefficient of variation is an indicator of the reliability of chemical tests. However, the coefficient of variation control chart (CV Chart) monitors the coefficient of variation, and the ability to detect small shift sizes is not good. This study uses a double sampling plan combined with a coefficient of variation control chart (DS CV chart) to improve the performance of CV Chart. A design model of DS CV chart is also created to optimize its parameters. The results of the study show that the good performance of DS CV chart in small shift detection.
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- 2020
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207. Improved ratio estimators of population mean using transformed variable in double sampling
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Nuanpan Lawson and Uraiwan Jaroengeratikun
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Variable (computer science) ,Double sampling ,Population mean ,020204 information systems ,Statistics ,0202 electrical engineering, electronic engineering, information engineering ,Estimator ,020201 artificial intelligence & image processing ,02 engineering and technology ,Mathematics - Published
- 2018
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208. Economic-statistical design of synthetic double sampling T2 chart
- Author
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Ming Ha Lee and Michael B. C. Khoo
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Statistics and Probability ,Optimal design ,Mathematical optimization ,021103 operations research ,Statistical design ,0211 other engineering and technologies ,02 engineering and technology ,Function (mathematics) ,01 natural sciences ,010104 statistics & probability ,Chart ,Double sampling ,0101 mathematics ,Mathematics - Abstract
An economic-statistical design of the synthetic double sampling (synDS) T2 chart is presented in this study. The cost function is minimized to obtain the optimal design parameters of the synDS T2 c...
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- 2018
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209. Estimation of a rare sensitive attribute in a stratified two-stage unrelated randomized response model by using Poisson probability distribution
- Author
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Amod Kumar, Gajendra K. Vishwakarma, and Gaje Singh
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Statistics and Probability ,Estimation ,05 social sciences ,Variance (accounting) ,Poisson distribution ,01 natural sciences ,Stratified sampling ,010104 statistics & probability ,symbols.namesake ,Character (mathematics) ,Double sampling ,0502 economics and business ,Statistics ,symbols ,Randomized response ,Stage (hydrology) ,0101 mathematics ,Statistics, Probability and Uncertainty ,050205 econometrics ,Mathematics - Abstract
The present article deals with the estimation of mean number of respondents who possess a rare sensitive character in presence of known and unknown proportion of a rare unrelated non-sensitive attribute by using the Poisson probability distribution in stratified random sampling as well as in stratified random double sampling. The variance of rare sensitive character is also derived under proportional and optimal allocation methods in stratified random sampling when stratum sizes are known and unknown. The properties of the suggested estimation procedures have been deeply examined. The proposed model is found to be dominant over Lee et al. [Estimation of a rare sensitive attribute in a stratified sample using Poisson distribution. Statistics. 2013;47:575–589] model. Numerical illustrations are presented to support the theoretical results. Results are analysed and suitable recommendations are put forward to the survey practitioners.
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- 2018
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210. Performance of Synthetic Double Sampling Chart with Estimated Parameters Based on Expected Average Run Length
- Author
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Huay Woon You
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Statistics and Probability ,Measure (data warehouse) ,021103 operations research ,Article Subject ,Average run length ,Computation ,0211 other engineering and technologies ,Process (computing) ,02 engineering and technology ,01 natural sciences ,Standard deviation ,010104 statistics & probability ,Chart ,Double sampling ,Statistics ,Control chart ,lcsh:Probabilities. Mathematical statistics ,0101 mathematics ,lcsh:QA273-280 ,Mathematics - Abstract
A synthetic double sampling (SDS) chart is commonly evaluated based on the assumption that process parameters (namely, mean and standard deviation) are known. However, the process parameters are usually unknown and must be estimated from an in-control Phase-I dataset. This will lead to deterioration in the performance of a control chart. The average run length (ARL) has been implemented as the common performance measure in process monitoring of the SDS chart. Computation of ARL requires practitioners to determine shift size in advance. However, this requirement is too restricted as practitioners may not have the experience to specify the shift size in advance. Thus, the expected average run length (EARL) is introduced to assess the performance of the SDS chart when the shift size is random. In this paper, the SDS chart, with known and estimated process parameters, was evaluated based on EARL and compared with the performance measure, ARL.
- Published
- 2018
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211. The economic and economic statistical designs of synthetic double sampling <font>X‾</font> chart
- Author
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Ming Ha Lee and Michael B. C. Khoo
- Subjects
Statistics and Probability ,Optimal design ,021103 operations research ,0211 other engineering and technologies ,02 engineering and technology ,01 natural sciences ,010104 statistics & probability ,Chart ,Double sampling ,Modeling and Simulation ,Statistics ,0101 mathematics ,Economic design ,\bar x and R chart ,Mathematics - Abstract
The purpose of this paper is to investigate the economic and economic statistical designs of the synthetic double sampling (DS) X‾ chart. The optimal design parameters for the economic design are d...
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- 2018
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212. Study on Non Response and Measurement Error using Double Sampling Scheme
- Author
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Sunil Kumar and Sandeep Bhougal
- Subjects
Scheme (programming language) ,Observational error ,Double sampling ,Computer science ,Algorithm ,computer ,computer.programming_language - Published
- 2018
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213. Visualizing and Assessing Acceptance Sampling Plans: The R Package AcceptanceSampling
- Author
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Andreas Kiermeier
- Subjects
operating characteristic ,oc curve ,defectivel defect ,non-conforming item ,non-conformity ,single sampling ,double sampling ,multiple sampling ,attributes sampling ,2-class ,variables S4 methods ,Statistics ,HA1-4737 - Abstract
Manufacturers and government agencies frequently use acceptance sampling to decide whether a lot from a supplier or exporting country should be accepted or rejected. International standards on acceptance sampling provide sampling plans for specific circumstances.The aim of this package is to provide an easy-to-use interface to visualize single, double or multiple sampling plans. In addition, methods have been provided to enable the user to assess sampling plans against pre-specified levels of performance, as measured by the probability of acceptance for a given level of quality in the lot.
- Published
- 2008
214. Extending a double sampling control chart for non-conforming proportion in high quality processes to the case of small samples.
- Author
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Joekes, Silvia, Smrekar, Marcelo, and Barbosa, Emanuel Pimentel
- Abstract
When production processes reach high quality standards they are known as high quality processes. In this situation, the conventional p charts (based on 3-sigma limits) used for monitoring non-conforming products have serious drawbacks in detecting changes in p due to excess of false alarm risk. In a previous paper, the authors showed a new p chart that provides a large improvement over the usual p chart in these situations. In this paper, authors propose a new corrected version of a double sampling (DS) control chart for monitoring the proportion p of non-conforming presented in the literature for large samples, in order to extend its applicability to the case of small samples. This procedure offers better statistical efficiency (in terms of the average run length) than the previous p charts, without increasing the sampling. Tables are provided to aid in the choice of DS parameters. The benefits of the corrected version of a DS chart for monitoring high-quality processes are illustrated with real data. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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215. Bayesian confidence intervals of proportion with misclassified binary data.
- Author
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Lee, Seung-Chun
- Abstract
Abstract: A Bayesian approach is considered for the interval estimation of a binomial proportion in doubly sampled data. The coverage probability and the expected width of the Bayesian confidence interval are compared with likelihood-related confidence intervals. It is shown that a hierarchical Bayesian approach provides relatively simple and effective confidence intervals. In addition, it is shown that Agresti–Coull type confidence interval, discussed by Lee and Choi (2009), can be justified by the Bayesian framework. [Copyright &y& Elsevier]
- Published
- 2013
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216. Reduced-Variance Methods for Detectability Correction of Population Abundance.
- Author
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Loehle, Craig and Arghami, Nasser
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VARIANCES , *PLANT populations , *ANIMAL populations , *SAMPLING (Process) , *ESTIMATION theory - Abstract
Detectability issues create uncertainty in field surveys of animal and plant populations. Detectability correction is one method employed to deal with this problem when there is reasonable certainty that detectability is roughly constant with time or in different areas. Two new reduced-variance estimators of detectability are introduced and evaluated for the case of using a detectability correction for new areas that are surveyed only once. The new estimates are unbiased or nearly unbiased and produce population estimates with smaller variance than the Lincoln–Petersen estimate. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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217. One-way analysis of proportions for misclassified binomial data.
- Author
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Rahardja, Dewi and Zhao, Yan D.
- Subjects
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BINOMIAL distribution , *DATA analysis , *GROUP theory , *MATHEMATICAL variables , *STATISTICAL sampling , *ERROR rates , *SIMULATION methods & models - Abstract
We consider data with a nominal grouping variable and a binary response variable. The grouping variable is measured without error, but the response variable is measured using a fallible device subject to misclassification. To achieve model identifiability, we use the double-sampling scheme which requires obtaining a subsample of the original data or another independent sample. This sample is then classified by both the fallible device and another infallible device regarding the response variable. We propose two Wald tests for testing the association between the two variables and illustrate the test using traffic data. The Type-I error rate and power of the tests are examined using simulations and a modified Wald test is recommended. [ABSTRACT FROM AUTHOR]
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- 2013
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218. Calibration of a burrow count index for the Indian desert jird, Meriones hurrianae.
- Author
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Ramesh, Divya, Home, Chandrima, Jhala, Yadvendradev, and Qureshi, Qamar
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MERIONES hurrianae ,CALIBRATION ,JIRDS ,RODENTS ,JACKKNIFE (Statistics) - Abstract
Population estimates, often difficult to acquire, warrantee the use of an index as an economical substitute for rapid assessments of populations. We estimated population size of the little known social, semi-fossorial Indian desert jird ( Meriones hurrianae) in Kachchh, Gujarat, India under closed population capture-mark-recapture (CMR) framework to calibrate a burrow count index for the species. A total of 147 individuals were trapped in 16 colonies using baited Sherman traps and the number of burrow entrances at each colony was recorded. Data from colonies with low number of captures were pooled to estimate capture probability using Huggins heterogeneity models with gender, site, body weight and age category as covariates in Program MARK. Colony sizes ranged from 2 to 46 individuals. The number of burrow entrances was calibrated against CMR-based population estimates using least squares regression ( n = 16, adjusted R = 0.96, t = 18.18, P < 0.001). The index was further validated using Jackknife (JK) analysis where JK-predicted population estimates strongly correlated with CMR estimates ( r = 0.96, P < 0.001). In habitats and climatic conditions similar to Kachchh and within the range of colony sizes sampled, our calibrated index can be a valuable and effective tool for large scale surveys of the desert jird, which occupies a keystone trophic level in the semi-arid ecosystem. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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219. Characterisation and optimal design of a new double sampling c chart
- Author
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Universitat Politècnica de València. Departamento de Estadística e Investigación Operativa Aplicadas y Calidad - Departament d'Estadística i Investigació Operativa Aplicades i Qualitat, Campuzano, Manuel J., Carrión García, Andrés, Mosquera, Jaime, Universitat Politècnica de València. Departamento de Estadística e Investigación Operativa Aplicadas y Calidad - Departament d'Estadística i Investigació Operativa Aplicades i Qualitat, Campuzano, Manuel J., Carrión García, Andrés, and Mosquera, Jaime
- Abstract
[EN] This paper proposes a new double sampling scheme for c control chart (DS-c), which was designed to improve the performance of c chart or to reduce the inspection cost. The mathematical expression required to do an exact evaluation of ARL and ASN is deduced. Further, a bi-objective genetic algorithm is implemented to obtain the optimal design of the DS-c scheme. This optimisation is aimed to simultaneously minimising the error probability type II and the ASN, guaranteeing a desired level for the error probability type I. A performance comparison between the double sampling (DS), fixed parameters (FP), variable simple size (VSS) and exponential weighted moving average (EWMA) schemes for the c chart is carried out. The comparison shows that with the implementation of DS-c scheme is obtained a significant reduction of the out of control ARL with a lower ASN respect to FP and a better ARL profile than VSS and EWMA.
- Published
- 2019
220. An 11-b 300-MS/s Double-Sampling Pipelined ADC With On-Chip Digital Calibration for Memory Effects.
- Author
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Miki, Takuji, Morie, Takashi, Ozeki, Toshiaki, and Dosho, Shiro
- Subjects
PIPELINED ADCs ,SAMPLING theorem ,SYSTEMS on a chip ,ANALOG-to-digital converter calibration ,COMPUTER storage devices ,COMPLEMENTARY metal oxide semiconductors ,CAPACITORS ,MATHEMATICAL models - Abstract
An 11-b 300-MS/s double sampling pipelined ADC with on-chip digital calibration for memory effects is presented. In double-sampling pipelined ADC architecture, memory effect of residual charge occurs due to sharing an op-amp between two channels of pipelined ADC. The proposed foreground calibration technique removes the memory effect error in digital domain without additional analog circuit. Thus, the technique simplifies the analog circuits, which extends the operation speed over 300∼MHz. The chip is fabricated in a 40 nm CMOS and occupies 0.42 mm^2 including digital calibration logic. The ADC consumes 40 mW from a 1.8 V supply, and FoM is 0.24-pJ/conversion-step. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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221. Sampling large landscapes with small-scale stratification.
- Author
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Bart, Jonathan, Dunn, Leah, Leist, Amy, and Sabin, Laura
- Subjects
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LANDSCAPES , *HABITATS , *PLANTS - Abstract
This study, carried out for the United States Bureau of Reclamation (BOR), demonstrated methods for surveying large landscapes using small-scale, habitat-based stratification, a common problem that has heretofore received little attention. The goal was to design a sampling plan for detecting change in the density of breeding birds of 6 species occurring along the Colorado River around and south of Lake Mead in the southwestern United States. The main problem in designing the study was that the focal species were concentrated in small, irregularly shaped patches of habitat. We partitioned the study area into >15,000 plots configured to enclose the high-quality habitat in the fewest possible plots with the constraint that plots could be surveyed in 1 morning by 1 person. Because of the irregular plot shapes and extremely dense vegetation, we used area searches to carry out the surveys. We used double-sampling, including a large sample of plots surveyed with a rapid method and a subsample of plots surveyed intensively, to estimate detection ratios. A simulation study helped allocate effort between rapid and intensive surveys and indicated that conducting 80 surveys per year would achieve high power to detect a 50% decline occurring during 20 years. This is one of the first studies to show how large landscapes can be sampled using small-scale stratification so that effort can be concentrated in the habitats of greatest interest. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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222. A 8 mW 72 dB ΣΔ-modulator ADC with 2.4 MHz BW in 130 nm CMOS.
- Author
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De Bock, Maarten and Rombouts, Pieter
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ELECTRONIC modulators ,INTEGRATORS ,COMPLEMENTARY metal oxide semiconductors ,SIGNAL-to-noise ratio ,INTEGRATED circuits - Abstract
A double-sampling split ΣΔ-ADC with bilinear integrators and a 7-level quantizer is presented. It achieves third order noise shaping with a second order modulator through quantization noise-coupling. The modulator is integrated in a 130 nm CMOS technology. For a clock frequency of 48 MHz and an oversampling ratio of 20 (2.4 MHz signal bandwidth), it achieves 72 dB DR and 68 dB SNR. The prototype consumes 8 mW from a 1.2 V voltage supply. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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223. Simulation modeling of a trawl-acoustic survey design for patchily distributed species
- Author
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Spencer, Paul D., Hanselman, Dana H., and McKelvey, Denise R.
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SIMULATION methods & models , *TRAWLING , *FISH populations , *SPECIES distribution , *BIOMASS , *FISHING , *FISH farming , *UNDERWATER acoustics - Abstract
Abstract: Spatially patchy populations present challenges for precise estimation of abundance from surveys, which typically result in high estimation errors compared to surveys of more evenly distributed species. In this study, we used simulations to evaluate the performance of the Trawl and Acoustic Presence/Absence Survey design (TAPAS) in reducing the variability in estimated biomass. This approach is a double sampling design in which high-density patches observed in a first phase using hydroacoustics are subsequently more intensively sampled (relative to non-patch areas) in a second phase using trawls and area-swept methods. Information on Gulf of Alaska Pacific ocean perch (Sebastes alutus), a patchily distributed rockfish species, was used to parameterize the simulations. The performance of the TAPAS design depends upon the degree to which high acoustic backscatter represents “patch” areas of high density and variability, as the relationship between backscatter and abundance of a given species can be affected by areas unavailable for sampling (i.e., the “dead zone”) and the contribution of multiple species to the backscatter intensity. With a strong relationship between backscatter intensity and density, the TAPAS design resulted in improved precision compared to simple random sampling (SRS). Additionally, more intensive sampling of the patches occurred when areas of high backscatter intensity were randomly distributed over space rather than located in spatially correlated clusters. However, with a weak relationship between backscatter intensity and density, the precision of the TAPAS design was not substantially larger than SRS. The potential improvement in precision when a strong relationship exists between backscatter intensity and fish density offers motivation to continue to refine relationships between underlying fish density, acoustic backscatter, and trawl catches. [Copyright &y& Elsevier]
- Published
- 2012
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224. Linking Forest Inventory and Analysis Ground Data to Maps: An Example for Nevada Pinyon-Juniper Forests.
- Author
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Chojnacky, David C., Prisley, Stephen P., and Miller, Sara R.
- Subjects
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FOREST surveys , *FORESTS & forestry , *PINYON pines , *JUNIPERS - Abstract
Using data from the USDA Forest Service's Forest Inventory and Analysis (FIA) program, we developed a mapping tool for displaying statistical forestland information. To develop this technique, we used data from Nevada's pinyon-juniper dryland forests, a major component of Nevada's forest cover important for food and wood sources, wildlife cover, and carbon storage. Land managers must grapple with issues, such as the health of these forests, the explanation of their encroachment into grasslands and shrublands, and causes of pinyon mortality associated with drought and bark-beetle activity. Our methodology con assist managers by offering the potential to map FIA statistics, such as carbon, volume, and stand structure to local conditions. FIA plots were classified according to the basal area occupied by dominant species groups. Employing this classification, we modeled the probability of pinyon-juniper occurrence at stand scale in Nevada from FIA data, using readily available remote sensing and geographic information system variables. Then, using the model with a Nevada-specific classification rule, we produced a cover mop for the state. Finally, we linked our model classification rule to FIA summary data to create a detailed statistical map of Nevada forest carbon distribution-a visual representation of FIA data on the landscape. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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225. SOME EXPONENTIAL ESTIMATORS IN SURVEY SAMPLING.
- Author
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Noor-ul-Amin, Muhammad and Hanif, Muhammad
- Subjects
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EXPONENTIAL functions , *DEMOGRAPHIC surveys , *MATHEMATICAL variables , *DEPENDENCE (Statistics) , *INDEPENDENCE (Mathematics) , *MEAN square algorithms , *SAMPLING errors , *STATISTICAL bias - Abstract
In this paper, some exponential type estimators have been proposed for estimating the finite population mean in double sampling using information on two auxiliary variables. The estimators have been discussed for independent and dependent samples under simple random sampling without replacement. The expressions for mean square errors and biases have been derived. An empirical study has been carried out to compare the efficiency of proposed estimators with some available estimators in literature. [ABSTRACT FROM AUTHOR]
- Published
- 2012
226. A class of chain ratio–product type estimators with two auxiliary variables under double sampling scheme.
- Author
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Choudhury, Sanjib and Singh, Bhupendra Kumar
- Subjects
MATHEMATICAL variables ,STATISTICAL sampling ,VARIANCES ,MATHEMATICAL analysis ,ESTIMATION theory - Abstract
Abstract: In this paper, a chain ratio–product type estimators has been developed for estimating population mean of the study variable using two auxiliary variables under double sampling scheme, when the information on another additional auxiliary character is available along with the main auxiliary character. The optimum property of the proposed strategy has been identified in two different cases with their variances. Theoretical and empirical studies have been done to demonstrate the efficiency of the proposed estimator over other estimators, which utilized the information on two auxiliary characteristics. [Copyright &y& Elsevier]
- Published
- 2012
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227. Optimal designing of an SkSP-V skip-lot sampling plan with double-sampling plan as the reference plan.
- Author
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Aslam, Muhammad, Balamurali, Saminathan, Jun, Chi-Hyuck, Ahmad, Munir, and Rasool, Mujahid
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PRODUCT quality , *SURFACE plates , *STRUCTURAL optimization , *QUALITY control , *ELECTRONIC equipment , *COMPARATIVE studies - Abstract
This paper deals with the optimal designing of a skip-lot sampling plan of type SkSP-V by considering the double-sampling plan as the reference plan. The design parameters are determined so as to minimize the average sample number while the specified producer's risk and the consumer's risks are satisfied. The tables are constructed by considering the various combinations of acceptable and limiting quality levels, and an example is given for illustration purpose. The advantages of the proposed plan over the conventional double-sampling plan are also discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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228. Test Procedures for Disease Prevalence with Partially Validated Data.
- Author
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Tang, Man-Lai, Qiu, Shi-Fang, Poon, Wai-Yin, and Tang, Nian-Sheng
- Subjects
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DISEASE prevalence , *MEDICAL research , *STATISTICAL sampling , *DATA , *SAMPLE size (Statistics) , *MEDICAL screening - Abstract
Investigating the prevalence of a disease is an important topic in medical studies. Such investigations are usually based on the classification results of a group of subjects according to whether they have the disease. To classify subjects, screening tests that are inexpensive and nonintrusive to the test subjects are frequently used to produce results in a timely manner. However, such screening tests may suffer from high levels of misclassification. Although it is often possible to design a gold-standard test or device that is not subject to misclassification, such devices are usually costly and time-consuming, and in some cases intrusive to the test subjects. As a compromise between these two approaches, it is possible to use data that are obtained by the method of double-sampling. In this article, we derive and investigate four test statistics for testing a hypothesis on disease prevalence with double-sampling data. The test statistics are implemented through both the asymptotic method suitable for large samples and approximate unconditional method suitable for small samples. Our simulation results show that the approximate unconditional method usually produces a more satisfactory empirical type I error rate and power than its asymptotic counterpart, especially for small to moderate sample sizes. The results also suggest that the score test and the Wald test based on an estimate of variance with parameters estimated under the null hypothesis outperform the others. An real example is used to illustrate the proposed methods. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
229. Combining data from two independent surveys: a model-assisted approach.
- Author
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Kim, Jae Kwang and Rao, J. N. K.
- Subjects
- *
STATISTICAL sampling , *ESTIMATION theory , *MATHEMATICAL variables , *STATISTICAL matching , *INFORMATION retrieval - Abstract
Combining information from two or more independent surveys is a problem frequently encountered in survey sampling. We consider the case of two independent surveys, where a large sample from survey 1 collects only auxiliary information and a much smaller sample from survey 2 provides information on both the variables of interest and the auxiliary variables. We propose a model-assisted projection method of estimation based on a working model, but the reference distribution is design-based. We generate synthetic or proxy values of a variable of interest by first fitting the working model, relating the variable of interest to the auxiliary variables, to the data from survey 2 and then predicting the variable of interest associated with the auxiliary variables observed in survey 1. The projection estimator of a total is simply obtained from the survey 1 weights and associated synthetic values. We identify the conditions for the projection estimator to be asymptotically unbiased. Domain estimation using the projection method is also considered. Replication variance estimators are obtained by augmenting the synthetic data file for survey 1 with additional synthetic columns associated with the columns of replicate weights. Results from a simulation study are presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
230. A 0.5-V 35- \mu W 85-dB DR Double-Sampled \Delta\Sigma Modulator for Audio Applications.
- Author
-
Yang, Zhenglin, Yao, Libin, and Lian, Yong
- Subjects
ELECTRONIC modulators ,AUDIO amplifiers ,SWITCHED capacitor circuits ,COMPLEMENTARY metal oxide semiconductors ,LOW voltage systems ,SIGNAL-to-noise ratio ,ENERGY consumption - Abstract
This paper presents a 0.5-V 1.5-bit double-sampled \Delta\Sigma modulator for audio applications. Unlike existing double-sampled designs, the proposed double-sampled \Delta\Sigma modulator employs an input-feedforward topology to reduce internal signal swings, thereby relaxing design requirements for the low-voltage building blocks and reducing distortion. Moreover, in order to avoid instability and noise shaping degradation, the proposed architecture restores the noise transfer function (NTF) of the double-sampled modulator to its single-sampled equivalent with the help of compensation loops. In the circuit implementation, the proposed fully-differential amplifier adopts an inverter output stage and a common-mode feedback (CMFB) circuit with a global feedback loop in order to reduce power consumption. A resistor-string-reference switch matrix based on a direct summation quantizer is used to simplify the analog compensation loop. The chip prototype has been fabricated in a 0.13-\mum CMOS technology with a core area of 0.57 \mm^2. The measured results show that when operating from a 0.5-V supply and clocked at 1.25∼MHz, the modulator achieves a peak signal-to-noise and distortion ratio (SNDR) of 81.7 dB, a peak signal-to-noise ratio (SNR) of 82.4 dB and a dynamic range (DR) of 85.0 dB while consuming 35.2\ \mu\W for a 20-kHz signal bandwidth. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
231. Airborne scanning LiDAR in a double sampling forest carbon inventory
- Author
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Stephens, Peter R., Kimberley, Mark O., Beets, Peter N., Paul, Thomas S.H., Searles, Nigel, Bell, Alan, Brack, Cris, and Broadley, James
- Subjects
- *
FOREST ecology , *INFORMATION storage & retrieval systems , *CARBON sequestration , *ENVIRONMENTAL monitoring , *ESTIMATION theory , *FOREST canopies , *REGRESSION analysis - Abstract
Abstract: To meet Kyoto Protocol obligations, New Zealand is required to estimate forest carbon stock change over the first commitment period (2008–2012). New Zealand has three subcategories of forest, namely: Natural forest; Pre-1990 forest; and Post-1989 forest. The Post-1989 forest carbon inventory undertaken in 2008 used discrete return airborne LiDAR and ground-based measurements of 0.06ha circular plots located on a 4-km×4-km grid. The national carbon stock estimate was based on a double sampling scheme consisting of 246 plots from which both ground and LiDAR data were obtained, supplemented with 46 additional plots assessed using only LiDAR. This paper describes the relationships established between carbon stocks estimated using ground-based measurements and LiDAR metrics. A regression model explaining 74% of the variation in total carbon was developed using LiDAR 30th percentile height (P30ht) and canopy cover (%Cover). The regression estimator improved the precision of the national carbon stock estimate in 2008 by 6% compared to the ground-based estimate. This inventory indicates that it is possible to reduce the cost of obtaining carbon stock estimates to a specified level of precision using a combination of ground-based and LiDAR measurements in a double sampling approach. The theoretical maximum improvement in precision expected in 2012, when additional LiDAR data are expected to be available, is 50–55%. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
232. Bayesian inference of a binomial proportion using one-sample misclassified binary data.
- Author
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Rahardja, Dewi and Zhao, Yan D.
- Subjects
BAYESIAN analysis ,BINOMIAL distribution ,POLYNOMIALS ,CONFIDENCE intervals ,BINARY number system - Abstract
Misclassified binary data result from using a fallible classifier for classifying units into two categories. If an infallible classifier is also available, a random subsample of this misclassified data can be further classified using the infallible classifier. For such data, the existing methods for exact confidence interval are too conservative, and the existing Bayesian credible interval suffers from computational difficulty. We derive a closed-form Bayesian algorithm which draws a posterior sample of the proportion parameter from the exact marginal posterior distribution. Our simulations show that our Bayesian algorithm is easy to implement and has nominal coverage. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
233. Bayesian credible sets for the risk difference in binomial data with a fallible classifier and a gold standard.
- Author
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Rahardja, Dewi and Zhao, Yan D.
- Subjects
- *
BAYESIAN analysis , *STATISTICAL sampling , *DATA analysis , *CLASSIFICATION , *DISTRIBUTION (Probability theory) , *MONTE Carlo method , *MATHEMATICAL statistics - Abstract
We consider two-sample binary data consisting of two independent studies. One study is the main study where individuals are classified using a fallible classifier prone to error; the other study is a validation study where individuals are classified using both the fallible classifier and a gold standard which does not misclassify individuals. For such data, we propose a Bayesian model for making statistical inference for all model parameters and particularly the risk difference. We derive a closed-form algorithm for sampling from the posterior distribution. We then illustrate our algorithm using a real data example and conduct Monte Carlo simulation studies to show that our algorithm performs very well under various scenarios. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
234. A Generalized Difference-cum-Ratio Type Estimator for the Population Mean in Double Sampling.
- Author
-
Jhajj, H.S. and Walia, GurjeetSingh
- Subjects
- *
REGRESSION analysis , *COMPUTER simulation , *STATISTICAL sampling , *POPULATION , *NUMERICAL analysis , *ESTIMATION theory , *LEAST squares - Abstract
Using double sampling technique, a generalized difference-cum-ratio type estimator has been proposed for estimating the population mean. The expressions for bias and mean square error of proposed estimator have been obtained. The conditions under which proposed estimator is better than the regression estimator and mean per unit estimator have also been obtained. The gain in efficiency over the existing ones have been illustrated numerically as well as graphically. Simulation study has also been done to support the results by generating data. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
235. A Generalized Difference-cum-Ratio Type Estimator for the Population Variance in Double Sampling.
- Author
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Jhajj, H. S. and Walia, G. S.
- Subjects
- *
GENERALIZATION , *ESTIMATION theory , *ANALYSIS of variance , *ERROR analysis in mathematics , *REGRESSION analysis , *MATHEMATICAL variables - Abstract
For estimating the population variance of variable under study, a generalized difference-cum-ratio type estimator has been proposed. Expressions for bias and mean square error have been obtained using random sampling at both the phases. The expressions have also been derived using simple random sampling at both the phases as a special case. Then the comparison has been made with the regression-type estimator and sample variance. Results have also been illustrated numerically and graphically. [ABSTRACT FROM AUTHOR]
- Published
- 2011
236. Vertical Point Sampling with a Camera.
- Author
-
Ducey, Mark J. and Kershaw, Jr., John A.
- Subjects
CAMERAS ,BASAL area (Forestry) ,FOREST measurement - Abstract
Vertical point sampling has seen relatively little use in practical forestry, in part because existing field techniques are difficult. We show how vertical point sampling can be implemented quickly and easily using a camera. We give tables and equations for calculating the height-squared factor, which plays a role similar to that of the basal area factor in horizontal point sampling. Some suggestions for choosing a height-squared factor are discussed, along with potential applications for further exploration. We illustrate the technique using a case study in southern Maine. Direct estimates with no statistically detectable bias were obtained using height-squared factors greater than 3. The results also suggested that the technique could be used as a correlate in double sampling for variables such as cubic volume, stand density index, and biomass, and possibly board foot volume as well. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
237. Bayesian Inference of Risk Ratio of Two Proportions Using a Double Sampling Scheme.
- Author
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Rahardja, Dewi and Young, DeanM.
- Subjects
- *
BAYESIAN analysis , *MATHEMATICAL statistics , *ALGORITHMS , *MONTE Carlo method , *PROBABILITY theory - Abstract
We consider Bayesian point and interval estimation for a risk ratio of two proportion parameters using two independent samples of binary data subject to misclassification. In order to obtain model identifiability, we apply a double sampling scheme. For the identifiable model, we propose a Bayesian method for statistical inference for a two proportion risk ratio. Specifically, we derive an easy-to-implement closed-form sampling algorithm to draw from the posterior distribution of interest. We demonstrate the efficiency of our algorithm for Bayesian inference via Monte Carlo simulation studies and using a real data example. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
238. Double-sampling control charts for attributes.
- Author
-
De Araújo Rodrigues, AuréliaAparecida, Epprecht, EugenioKahn, and De Magalhães, MaysaSacramento
- Subjects
- *
STATISTICAL sampling , *EXPERIMENTAL design , *SAMPLE size (Statistics) , *MATHEMATICAL optimization , *MATHEMATICAL analysis , *STATISTICS - Abstract
In this article, we propose a double-sampling (DS) np control chart. We assume that the time interval between samples is fixed. The choice of the design parameters of the proposed chart and also comparisons between charts are based on statistical properties, such as the average number of samples until a signal. The optimal design parameters of the proposed control chart are obtained. During the optimization procedure, constraints are imposed on the in-control average sample size and on the in-control average run length. In this way, required statistical properties can be assured. Varying some input parameters, the proposed DS np chart is compared with the single-sampling np chart, variable sample size np chart, CUSUM np and EWMA np charts. The comparisons are carried out considering the optimal design for each chart. For the ranges of parameters considered, the DS scheme is the fastest one for the detection of increases of 100% or more in the fraction non-conforming and, moreover, the DS np chart is easy to operate. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
239. Calibration of the Delaware Rapid Assessment Protocol to a Comprehensive Measure of Wetland Condition.
- Author
-
Sifneos, Jean C., Herlihy, Alan T., Jacobs, Amy D., and Kentula, Mary E.
- Abstract
The importance of monitoring and assessment to the management and protection of wetlands has become widely recognized. Wetland assessments are made at multiple intensity levels based on data quality, the application scale, available resources, and the level of effort involved in data collection. We used multiple regression to calibrate the output of a rapid assessment method to condition scores derived from a comprehensive assessment. Data collected at riverine, depression, and flat wetlands in the Nanticoke and Inland Bays watersheds of Delaware and Maryland were used to calibrate the Delaware Rapid Assessment Protocol to an Index of Wetland Condition (IWC) derived from hydrogeomorphic variables. The resulting calibrated rapid condition score was highly correlated with the intense IWC score in each wetland type ( r = .88 for riverine, r = .82 for depressions and flats). The calibration methodology was also robust with respect to different statistical cutoff values and model selection methods. Our approach provides a quantitative alternative to using best professional judgment to determine rapid assessment scoring coefficients. Additionally, when rapid and comprehensive methods are correlated, double sampling, a statistical sampling method, can be used to increase the overall sample size resulting in either increased precision of condition estimates or lower sampling costs. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
240. ESTIMATING THE ABUNDANCE OF NESTING RUSTY BLACKBIRDS IN RELATION TO WETLAND HABITATS IN ALASKA.
- Author
-
Matsuoka, Steven M., Shaw, David, and Johnson, James A.
- Subjects
- *
BLACKBIRDS , *WETLAND birds , *NEST building , *HABITAT selection , *QUANTITATIVE research - Abstract
The article presents a study which examines the total number of nesting Rusty Blackbirds (Euphagus carolinus) in boreal wetland habitats in Anchorage and Tanana Flats in Alaska. The study uses double sampling, and statistical analyses to estimate the number of pairs of nesting Rusty Blackbirds in Anchorage and Tanana Flats in 2007 and 2008. The result shows that habitat selection has been easily detected in Anchorage than Tanana Flats.
- Published
- 2010
- Full Text
- View/download PDF
241. Estimation of mean in presence of non-response using two phase sampling scheme.
- Author
-
Singh, Housila and Kumar, Sunil
- Subjects
MATHEMATICAL variables ,NONRESPONSE (Statistics) ,APPROXIMATION theory ,ESTIMATION theory ,ANALYSIS of variance ,SAMPLE variance - Abstract
This paper considers the problem of estimating the population mean using information on an auxiliary variable in presence of non-response. Some modified ratio, product and regression estimators in double sampling have been suggested and their properties are studied. It is shown that to the first degree of approximation, estimators based on estimated optimum values have the same variance as that of the optimum estimators. An empirical study is carried to judge the merits of the suggested estimators over conventional unbiased estimator and other known estimators. Both theoretical and empirical study results present the soundness and usefulness of the suggested estimators in practice. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
242. Linking local ecological knowledge and habitat modelling to predict absolute species abundance on large scales.
- Author
-
Anadón, José Daniel, Giménez, Andrés, and Ballestar, Rubén
- Subjects
ANIMAL species ,HABITATS ,CALIBRATION ,TESTUDINIDAE ,TESTUDO graeca ,COST effectiveness ,WILDLIFE conservation ,SHEPHERDS - Abstract
Assessing the spatial structure of abundance of a species is a basic requirement to carry out adequate conservation strategies. However, existing attempts to predict species abundance, particularly in absolute units and on large scales, are scarce and have led to weak results. In this work we present a scheme to obtain, in an affordable way, a predictive model of absolute animal abundance on large scales based on the modelling of data obtained from local ecological knowledge (LEK) and its calibration. To exemplify this scheme, we build and validate a predictive absolute abundance model of the endangered terrestrial tortoise Testudo graeca in Southeast Iberian Peninsula. For that purpose, we collected distribution and relative abundance data of T. graeca using a low cost methodology, such as LEK, by means of interviewing shepherds. The information from LEK was employed to build a predictive habitat-based model of relative abundance. The relative abundance model was transformed into an absolute abundance model by means of calibration with a classical absolute abundance sampling method such as distance sampling. The obtained absolute abundance model predicted the observed absolute abundances values well in independent locations when compared with other works (R
2 = 36%) and thus can offer a cost-effective predictive ability. Our results show that reliable habitatbased predictive maps of absolute species abundance on regional scales can be obtained starting from low cost sampling methods of relative abundance, such as LEK, and its calibration. [ABSTRACT FROM AUTHOR]- Published
- 2010
- Full Text
- View/download PDF
243. A LOW-VOLTAGE LOW-POWER 10-BIT 200 MS/S PIPELINED ADC IN 90 NM CMOS.
- Author
-
ABDINIA, SAHEL and YAVARI, MOHAMMAD
- Subjects
- *
COMPLEMENTARY metal oxide semiconductors , *ELECTRIC potential , *PIPELINE computers , *ELECTRONIC amplifiers , *COMPARATOR circuits - Abstract
This paper presents a low-power 10-bit 200 MS/s pipelined ADC in a 90 nm CMOS technology with 1 V supply voltage. To decrease the power dissipation efficiently, a new architecture using a combination of two power reduction techniques named double-sampling and opamp-sharing has been used to reduce the power consumption significantly, without any degradation in the performance of the ADC. In addition, the stage scaling technique has been applied to the ADC efficiently, and two-stage class A/AB and class A amplifiers and dynamic comparators have been used in sample and hold and sub-ADCs. According to HSPICE simulation results, the 10-bit 200 MSample/s pipeline ADC with a 9.375 MHz, 1-VP-P,diff input signal in a 90 nm CMOS process achieves a SNDR of 58.5 dB while consuming only 30.9 mW power from a 1 V supply voltage. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
244. A Correction Note on Improvement in Variance Estimation Using Auxiliary Information.
- Author
-
Grover, LovleenKumar
- Subjects
- *
ESTIMATION theory , *VARIANCES , *ERROR analysis in mathematics , *NUMERICAL analysis , *MATHEMATICAL statistics - Abstract
Shabbir and Gupta (2007) introduced an exponential ratio-type estimator for the population variance and compare its mean square error with mean square error of some of the existing estimators. But unfortunately, the expression of mean square error of their proposed estimator is incorrect and hence the comparison based on incorrect mean square error, carried by them, is wrong. In the present article, the author provides the correct expression of the mean square error, up to first order of approximation, of the same estimator. A comparison has been made by taking the corrected expression of mean square error. The corresponding exponential ratio-type estimator for the population variance, under double sampling technique, is also proposed which followed by a comparison. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
245. Regression estimation techniques with remote sensing: a review and case study.
- Author
-
Haack, Barry and Rafter, Ann
- Subjects
- *
ESTIMATION theory , *ARTIFICIAL satellites , *REGRESSION analysis , *ORYZA - Abstract
With the relatively recent widespread availability of operational fine spatial resolution imagery from satellites, there is more opportunity to conduct spatial sampling with combinations of spatial resolution data. This method is generally called regression estimation. Regression estimation consists of first using a coarser spatial resolution sensor over a large area. For selected samples, a second delineation is done with a finer spatial resolution system which is presumed to be more accurate. A statistical comparison of the two estimates for the selected sample areas is made and if a suitable relationship exists, a correction factor can be determined and applied to the full study area. This manuscript reviews the regression estimation process and provides a case study. The case study used the technique to determine the extent of the winter rice crop in Bangladesh with Landsat data and statistics provided for local administrative units by agricultural agents. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
246. Double Sampling
- Author
-
Capinera, John L., editor
- Published
- 2008
- Full Text
- View/download PDF
247. PROBABILITY OF DETECTION OF NESTS AND IMPLICATIONS FOR SURVEY DESIGN.
- Author
-
Smith, Paul A., Bart, Jonathan, Lanctot, Richard B., McCaffery, Brian J., and Brown, Stephen
- Subjects
- *
PROBABILITY theory , *SHORE birds , *BIRD nests , *ORNITHOLOGY , *BIRD watching , *EXPERIMENTAL design - Abstract
The article presents a study on the probability of detection of nests and its significance to survey design. The researchers used a double sampling method to predict closely complete counts of birds in the intensively surveyed plots by calculating the probability of detecting active shorebird nests. Results show that the probability varies considerably by species and it suggests that the method is likely to be met for bird's nests that survive over several visits.
- Published
- 2009
- Full Text
- View/download PDF
248. Plug-In Two-Stage Normal Density Estimation Under MISE Loss: Unknown Variance.
- Author
-
Mukhopadhyay, Nitis and Pepe, William
- Subjects
- *
DENSITY functionals , *DISTRIBUTION (Probability theory) , *MULTILEVEL models , *ESTIMATION theory , *INTEGRAL theorems , *STATISTICAL sampling - Abstract
Consider independent observations X1, X2,... having a common normal probability density function [image omitted] with - ∞ < x < ∞ and unknown variance σ2 ( > 0). We propose to estimate f(x;σ2) by a plug-in maximum likelihood (ML) two-stage estimator under the mean integrated squared error (MISE) loss function. Our goal is to make the associated risk not to exceed a preassigned positive number c, referred to as the risk-bound. Because no fixed-sample-size methodology would handle this estimation problem, we design an appropriate two-stage estimation methodology that is shown to satisfy the asymptotic (i) first-order efficiency property (Theorem 2.1), (ii) first-order risk-efficiency property (Theorem 2.2), as well as (iii) second-order efficiency property (Theorem 2.3). The performances of the proposed methodology for small, moderate, and large sample sizes are examined with the help of simulations. We have noticed some limited robustness of the proposed methodology under mixture-normal population densities, in which case the asymptotic second-order efficiency property (Theorem 3.1) is shown. Illustrations are included with real data and analysis. Overall, we feel that the proposed two-stage plug-in density estimation methodology performs remarkably well. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
249. Using high-resolution satellite imagery and double sampling as a cost-effective means of collecting forest inventory data - the case of Hans Kanyinga Community Forest, Namibia.
- Author
-
Kamwi, J. M. and Kätsch, C.
- Subjects
PHOTOGRAMMETRY ,ARTIFICIAL satellites ,REMOTE-sensing images ,FORESTS & forestry ,REGRESSION analysis ,STATISTICAL correlation - Abstract
The present study deals with the use of high-resolution satellite imagery in forest inventory of the open savanna woodlands of southern Africa. The study was carried out in Hans Kanyinga Community Forest, north-eastern Namibia. A two-phase (double) sampling design was used to estimate the variables of interest, namely stand volume, stand density and diameter distribution. QuickBird satellite images were used to extract auxiliary variables (image data), such as photogrammetric crown diameter and number of stems, using visual interpretation and measuring tools offered by Erdas 8.7 geographic imaging software. Field inventory data (terrestric data) collected in 2002 were used to obtain the terrestric data. Stepwise regression and correlation analysis between satellite imagery and field data was carried out and the results were moderate. The stand volume model explained 56%, the stand density model 81% and the diameter distribution model 43% of the variation. Cost-efficiency assessment of double sampling with regression estimators showed a considerable reduction in inventory costs by up to 24% compared to a traditional forest inventory method in Hans Kanyinga Community Forest. Double sampling was found to be cost-efficient when the proportion of variability of the models was higher than 27%. The inventory concept showed potential in providing information required both at the higher and lower levels of forest management. Follow up research is required. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
250. The Need for Double-Sampling Designs in Survival Studies: An Application to Monitor PEPFAR.
- Author
-
An, Ming-Wen, Frangakis, Constantine E., Musick, Beverly S., and Yiannoutsos, Constantin T.
- Subjects
- *
HIV , *AIDS , *EPIDEMICS , *PATIENTS , *MORTALITY , *METHODOLOGY - Abstract
In 2007, there were 33.2 million people around the world living with HIV/AIDS ( UNAIDS/WHO, 2007 ). In May 2003, the U.S. President announced a global program, known as the President's Emergency Plan for AIDS Relief (PEPFAR), to address this epidemic. We seek to estimate patient mortality in PEPFAR in an effort to monitor and evaluate this program. This effort, however, is hampered by loss to follow-up that occurs at very high rates. As a consequence, standard survival data and analysis on observed nondropout data are generally biased, and provide no objective evidence to correct the potential bias. In this article, we apply double-sampling designs and methodology to PEPFAR data, and we obtain substantially different and more plausible estimates compared with standard methods (1-year mortality estimate of 9.6% compared to 1.7%). The results indicate that a double-sampling design is critical in providing objective evidence of possible nonignorable dropout and, thus, in obtaining accurate data in PEPFAR. Moreover, we show the need for appropriate analysis methods coupled with double-sampling designs. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
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