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Aim: To compare the amount of extruded debris with three endodontic NiTi engine driven systems, Protaper Next, Hyflex CM and EdgeFile X7. Material and Methods: A total number of 42 freshly extracted human premolars were selected. Teeth were divided randomly into three equal groups (14 teeth each group) according to type of Ni-Ti rotary file system; (A) Protaper Next, (B) Hyflex CM and (C) EdgeFile X7. Standard Access cavity prepared and checked for patency using K file #10 and #15. Root canal instrumentation on the single canal lower premolars was done. Debris was collected after root canal instrumentation in pre-weighed Eppendorf tubes. The Eppendorf tubes were weighed 2 times on the analytical balance. First weight: Before instrumentation. Second weight: After evaporation of moisture and irrigant and incubation. Welch test was used for comparison between the three groups. Results: There was no statistically significant difference between the amounts of debris extrusion of the three groups Conclusion: All endodontic rotary instruments tested produced apical extrusion of debris.

Since COVID-19 pandemic entered Indonesia, mental health experts have also investigated the increase in psychological problems, one of which is anxiety. The fear of being infected or unknowingly infecting other people is a major source of anxiety during COVID-19 pandemic. This study aims to describe the differences in early adult anxiety during COVID-19 in terms of gender. This study is a comparative study at the early adult development stage in Indonesia, obtained through random sampling. The sample of this study was 206 people (male = 66; female = 140). The analysis technique used is the Welch Test on the Rasch model with the help of WINSTEPS Version 3.73. The analysis showed that there was no difference in anxiety during COVID-19 between male and female early adulthood. This condition is caused by early adulthood male and female depending on the internet and smartphones to find information when quarantining at home, increasing feelings of anxiety about being infected with COVID-19. The implementation of guidance and counseling is discussed further

PurposeTo characterize the prevalence of work-related musculoskeletal disorders (MSD), symptoms, and risk factors among ophthalmologists.MethodsAn online survey was distributed to ophthalmologist members of the Maryland Society of Eye Physicians and Surgeons. The survey consisted of 34 questions on respondent demographics, practice characteristics, pain, and effects of MSD on their practice patterns. Participants were excluded if they were not ophthalmologists or if they had MSD symptoms prior to the start of their ophthalmology career. Demographics and practice patterns were compared for those with or without MSD symptoms using the Welch t test and the Fisher exact test.ResultsThe survey was completed by 127 of 250 active members (response rate, 51%). Of the 127, 85 (66%) reported experiencing work-related pain, with an average pain level of 4/10. With regard to mean age, height, weight, years in practice, number of patients seen weekly, and hours worked weekly, there was no difference between respondents reporting pain and those without. Those reporting MSD symptoms spent significantly more time in surgery than those who did not (mean of 7.9 vs 5.3 hours/week [P < 0.01]). Fourteen percent of respondents reported plans to retire early due to their symptoms.ConclusionsA majority of respondents experienced work-related MSD symptoms, which was associated with time spent in surgery. Modifications to the workplace environment focusing on ergonomics, particularly in the operating room, may benefit ophthalmologists.

Although unsuccessful bids are usually discarded once the bids are opened under the typical lowest-price sealed-bid project award auction environment, considering efforts and resources expended by responsive and responsible bidders, it is likely that not only a successful bid but also unsuccessful bids can convey important information about the project at hand. This article documents an effort to answer the question that whether projects that receive more dispersed estimates at the bidding stage are more likely to experience greater project cost changes. Taking collective intelligence as the theoretical framework, a total of 210 projects conducted by the Ohio Department of Transportation between 2008 and 2018 were analyzed to investigate the relationship between the coefficients of variation of bids and project final costs. It was found that large projects with above-average coefficients of variation of bids showed greater deviations from original award amounts than large projects with below-average coefficients of variation. The finding enables project owners to study the projects before execution by recouping valuable insights from the community of bidders on the possibility of greater project cost changes faced by the planned projects without complex and mathematically rigorous models.

In this study, we analyzed the changes in the average daily, monthly, seasonal, and annual surface air temperatures based on the temperature data obtained from seven stations (1 January 2005&ndash, 31 December 2019, 15 years) belonging to the central Baltic area (Stockholm, Tallinn, Helsinki, Narva, P&auml, rnu, Tartu, and V&otilde, ru). The statistical analysis revealed that there was a strong correlation between the daily average surface air temperature of the studied cities (range: 0.95&ndash, 0.99). We analyzed the frequency distribution of the average surface air temperatures in addition to the Kruskal&ndash, Wallis and Dunn&rsquo, s tests (significance level of 0.05) to demonstrate that the difference in air temperatures between Narva, Tallinn, Tartu, and Stockholm are critical. The Welch&rsquo, s -test (significance level 0.05), used to study the differences in the average monthly air temperature of the cities in question, showed that the surface air temperatures in Stockholm do not differ from Tallinn air temperatures from May to August. However, the surface air temperatures of Narva were similar to those of Tallinn in September. According to our results, the trends in the changes of monthly average surface air temperatures have a certain course during the year (ranging from 1.8 &deg, C (Stockholm) to 4.5 &deg, C (V&otilde, ru and Tartu) per decade in February). During the entire study period, in addition to February, the surface air temperature increased in all the studied cities in March, May, June, and December, and the surface air temperature did not increase in January or from July to October. During the study period, the average annual surface air temperature in the cities of the central Baltic area increased by 0.43 &deg, C per decade. The results also confirm that the surface air temperature in the study area is changing differently in different cities. The acceleration of the surface air temperature is very alarming and requires a significant intensification of the measures taken to slow down the temperature rise.

Researchers are generally required to report and interpret effect sizes and associated confidence intervals. When comparing two independent groups, the most commonly used estimator of effect size is Cohen’s ds where sample mean difference is divided by the pooled standard deviation. However, computing the pooled error term is not valid when both groups do not share common population variances. Furthermore, the assumption of equal population variances is unlikely in many psychological fields. Consequently, researchers shift to the use of Welch’s t-test over Student’s t-test in the context of hypothesis testing. Meanwhile, the question which effect size to report when equal variances are not assumed remains open. Based on Monte Carlo simulations, we compare Hedges’ gs (i.e. Cohen’s ds with correction for bias) to Glass’s gs, Shieh’s gs and Hedges’ g_s^*. Comparisons are made under normality as well as under realistic deviations from the assumptions of normality and equal variances. Although it is not directly related with Welch’s t-test (unlike Shieh’s gs), we recommend the use of Hedges’ g_s^* because it shows better properties than all other estimators. Practical recommendations, R package and Shiny App in order to compute effect size estimators and confidence intervals are provided.

A transformation of the Welch statistic to compare means is proposed to correct skewness and kurtosis of parent populations. The results show that this transformation seems to improve the performance of the test in heavy-tailed distributions more than other transformations focused only on skewness. The proposed test outperforms the Welch test in asymmetric heavy-tailed distributions with high heteroscedasticity and it behaves better than the Johnson’s transformation trimmed mean Welch test in normal, near-normal and light-tailed distributions. It may also be a better option when some of the distributions are heavy-tailed and some light-tailed.

Objective: The aim of the study was to compare and evaluate Hyflex CM files and M-Pro files versus Protaper Next files regarding the amount of apically extruded debris in the mesial root canals of mandibular molars.Methodology: Sixty three human permanent mandibular molars were utilized in the study. Empty Eppendorf tubes were weighed using an analytical balance three times and an average weight was calculated (W1). Then, a hole was created in the stopper of the Eppendorf tubes and mesial roots were inserted. The roots were randomly assigned into 3 groups according to the instrumentation technique used: Group I: Protaper Next (n=21), Group II: Hyflex (n=21) and Group III: M-Pro (n=21). Distilled water was used as an irrigant in all groups. After instrumentation, the vials were placed in an incubator for 3 days and the apically extruded debris collected in the Eppendorf tubes were weighed again (W2) after instrumentation. Welch test was used for comparison between the three groups.Results: There was no statistically significant difference between the amount of debris extrusion of the three groups (P=0.204). Conclusion: Within the limitation of this study it was concluded that all systems were associated with extrusion of debris.

The current study aims at discriminating cotton and woolen textile fibers from dye using UV-Vis spectroscopy and chemometrics methods. For extraction of the dye from fibers, seven solvent systems have been used, and different extraction conditions have also been tested. Two different approaches, i.e., a visual comparison of peaks and chemometric analysis, have been proposed to differentiate between the textile fibers. The comparison of peaks obtained through UV-Vis spectra provides the discrimination power of 83.6% for cotton fibers and 94.3% for the woolen fibers. However, the incorporation of chemometrics has further improved the discrimination power to 100% for cotton and 98.1% for woolen fibers. The discrimination of 100% is achieved with nonsignificant values of the Welch's t-test, which illustrates that all samples are discriminated.

El plagio académico es una práctica común entre estudiantes universitarios. Tradicionalmente esta temática ha sido abordada a través de estudios que determinan los factores generadores de la misma, sin ahondar en estrategias efectivas que prevengan dichas prácticas. Por tanto, para este estudio se utilizó una estrategia novedosa llamada i_map, que reduce el plagio académico a través del fortalecimiento de las habilidades de búsqueda y manejo de información, documentación del proceso de investigación y generación de ideas propias por parte del estudiante.El objetivo de este estudio es determinar la efectividad del i_map en la prevención del plagio académico y compararla con estrategias tradicionales como el reforzamiento en el uso de paráfrasis y citas textuales. La investigación fue desarrollada en tres espacios pedagógicos de la Carrera de Ciencias Naturales del CUED-UPNFM, cada espacio fue diferenciado según el tipo de estrategia utilizada (i_map, talleres de paráfrasis y citas textuales, equipo control) para la elaboración de ensayos académicos. En total fueron analizados 74 ensayos. El análisis de los datos fue realizado a través de un ANOVA de factor único y Welch test. Los niveles más bajos de plagio (p=0.0003246) y los valores medios más altos de fuentes académicas citadas (p=0.0100) fueron registrados en los trabajos de los estudiantes que utilizaron el i_map. Este estudio concluye la efectividad, estadísticamente significativa, del uso del i_map en la prevención de plagio académico, por lo que sugerimos la inclusión de esta estrategia como herramienta para prevenir dicha práctica y a la vez mejorar la redacción de asignaciones escritas.

Background: On February 26, 2020, the first case of coronavirus disease 2019 (COVID-19) was detected in Israel. The Ministry of Health (MoH) instructed people to take isolation measures and restrict their movement. Similarly, there was a gradual decrease in the number of visits to our emergency department (ED). Objectives: To describe the decline in the referrals to the ED and in-hospital beds occupancy during the COVID-19 pandemic and to compare it to the H1N1 2009 pandemic. Methods: Employing a cross-sectional epidemiologic study, the pattern of visits to the ED during the COVID-19 was compared with the pattern of visits during the 2009 H1N1 pandemic, as well as a year without a pandemic. The data was adjusted to consider changes in population size. The Welch t test for unpaired, unequal samples was used to analyze the data. Results: Within 2 months of the COVID-19 outbreak, the average number of visits to the ED dropped by 30.2% and the hospital occupancy by 29.2% (a minimum of 57%), compared to the same period, the year before. In comparison to the same period during the H1N1 outbreak, we witnessed a significant decline in the number of visits to the ED during the COVID-19 outbreak. Conclusion: The behavior of people during the COVID-19 pandemic was different from their behavior during the H1N1 pandemic. People seemed to avoid visiting the ED. The boundary between precaution and panic in the generation of the media could be very thin. Decision-makers must take this into account.

Objectives To better characterize the formation of false memories in older adults, we conducted a study using a French adaptation of the misinformation paradigm from Loftus, Levidow, and Duensing (1992). We aimed to show higher false memory production in older than in younger adults. Method One hundred and four younger adults (18–30 years) and 104 older adults (70–95 years) took part in the study. Participants were presented with a misinformation paradigm through the viewing of a short video followed by a questionnaire containing misinformation about the film. After a short delay (45 min), they performed a recognition task. Results Contrary to our hypothesis, the results analyzed with a Welch t test did not reveal a greater misinformation effect in older adults than in younger adults. Results were reanalyzed using the equivalence test which indicated that younger and older adults are statistically equivalent and not statistically different. Discussion The equivalence test helped to clarify the contradictory results of the literature. Furthermore, such results show the interest to reconsider misinformation effect in aging.

Purpose: To assess the impact of COVID-19 on the overall volume of IR outpatient-based evaluation and management encounters (E&M) and to demonstrate the role of telehealth in offsetting the loss of volume caused by COVID-19 Materials and Methods: A retrospective review of IR E&M in a large academic health system between January 6, 2020 and August 23, 2020, was conducted using the same time period in 2019 as a historical control. IR encounters were collected by gathering the weekly volume of submitted E&M current procedural technology (CPT) codes from the IR division. IR encounters were classified as outpatient or telehealth E&M. The E&M volume in 2019 was used as a historical control. Data were divided into three periods: pre-surge (January 6–March 15, 2020), surge (March 16–June 7, 2020), and recovery (June 8–August 23, 2020). The mean encounters per week during the surge and recovery periods were compared to the pre-surge baseline using a Welch t test for 2020 data, and the same comparison was made for 2019 data for a historical control. Results: During the surge period, outpatient E&M volume, inclusive of telemedicine, fell by 55.8% relative to the pre-surge 2020 baseline. The volume grew steadily during the recovery period but remained 19.8% below pre-surge 2020 levels. The surge and recovery mean weekly E&M volume was significantly different from the equivalent periods in 2019 (P < 0.001 and P = 0.02, respectively). During the surge, telemedicine comprised 44.6% of the total outpatient E&M. The contribution of telemedicine gradually fell over the recovery period, comprising just 11.5% in the final week of the study, and 16.7% during the recovery. Outpatient E&M reached a nadir during the week of April 13th, reflecting a 70.6% decline relative to the same period in 2019. The recovery period demonstrated a gradual increase in outpatient E&M with a decline in telehealth encounters balanced by a growth of in-person visits. During the last week of the recovery period (week of 8/17), outpatient in-person E&M had recovered to 2019 levels, and with the inclusion of telehealth exceeded E&M in 2019 for the same period by 93.3%. Conclusions: Telemedicine becomes an important way to maintain outpatient E&M volume in the event of a pandemic when social distancing and stay-at-home orders preclude face-to-face visits. Revenue from outpatient E&M may help bridge the gap until resumption of elective procedures and recovery of procedural case volume.

Nguyen et al. (2016) offered advice to researchers in the commonly-encountered situation where they are interested in testing for a difference in central tendency between two populations. Their data and the available literature support very simple advice that strikes the best balance between ease of implementation, power and reliability. Specifically, apply Satterthwaite’s test, with preliminary ranking of the data if a strong deviation from normality is expected, or is suggested by visual inspection of the data. This simple guideline will serve well except when dealing with small samples of discrete data, when more sophisticated treatment may be required.

This study investigates how outliers of different magnitude impact the robustness of the twosample t-test. A simulation study approach is used to analyze the behavior of type I error rates when outliers are added to generated data. Outliers may distort parameter estimates such as the mean and variance and cause misleading test results. Previous research has shown that Welch’s ttest performs better than the traditional Student’s t-test when group variances are unequal. Therefore these two alternative statistics are compared in terms of type I error rates when outliers are added to the samples. The results show that control of type I error rates can be maintained in the presence of a single outlier. Depending on the magnitude of the outlier and the sample size, there are scenarios where the t-test is robust. However, the sensitivity of the t-test is illustrated by deteriorating type I error rates when more than one outlier are included. The comparison between Welch’s t-test and Student’s t-test shows that the former is marginally more robust against outlier influence.

The Test Vector Leakage Assessment (TVLA) methodology is a qualitative tool relying on Welch’s T-test to assess the security of cryptographic implementations against side-channel attacks. Despite known limitations (e.g., risks of false negatives and positives), it is sometimes considered as a pass-fail test to determine whether such implementations are “safe” or not (without clear definition of what is “safe”). In this note, we clarify the limited quantitative meaning of this test when used as a standalone tool. For this purpose, we first show that the straightforward application of this approach to assess the security of a masked implementation is not sufficient. More precisely, we show that even in a simple (more precisely, univariate) case study that seems best suited for the TVLA methodology, detection (or lack thereof) with Welch’s T-test can be totally disconnected from the actual security level of an implementation. For this purpose, we put forward the case of a realistic masking scheme that looks very safe from the TVLA point-of-view and is nevertheless easy to break. We then discuss this result in more general terms and argue that this limitation is shared by all “moment-based” security evaluations. We conclude the note positively, by describing how to use moment-based analyses as a useful ingredient of side-channel security evaluations, to determine a “security order”.

This article proposes a useful extension of the ANOVA F-test for examining mean differences for evaluating the comparability of standardized mean effects. The equivalence procedure presumably suffers from the same disadvantage as the traditional ANOVA F-statistic regarding the violations of homogeneous variance assumption. In view of the absence of vital clarification for theory development and supportive technique, this article provides a critical exposition of the extended Welch test for the equivalence of standardized means. To enhance the usefulness of equivalence testing, the theoretical properties and practical implications of the Welch-type procedure are demonstrated. Moreover, the corresponding power and sample size algorithms are described for advance planning of equivalence studies. Despite the approximate nature, the accuracy of Type I error rate, statistical power, and sample size calculations of the suggested equivalence test is justified under a wide range of model configurations. The proposed procedures are demonstrated with the data of a clinical trial regarding the comparative study of four antihypertensive treatments. A complete set of computer codes is presented to calculate the corresponding critical values, p-values, power levels, and sample sizes for data analysis and design planning of equivalence studies.

The parametric Welch $t$-test and the non-parametric Wilcoxon-Mann-Whitney test are the most commonly used two independent sample means tests. More recent testing approaches include the non-parametric, empirical likelihood and exponential empirical likelihood. However, the applicability of these non-parametric likelihood testing procedures is limited partially because of their tendency to inflate the type I error in small sized samples. In order to circumvent the type I error problem, we propose simple calibrations using the $t$ distribution and bootstrapping. The two non-parametric likelihood testing procedures, with and without those calibrations, are then compared against the Wilcoxon-Mann-Whitney test and the Welch $t$-test. The comparisons are implemented via extensive Monte Carlo simulations on the grounds of type I error and power in small/medium sized samples generated from various non-normal populations. The simulation studies clearly demonstrate that a) the $t$ calibration improves the type I error of the empirical likelihood, b) bootstrap calibration improves the type I error of both non-parametric likelihoods, c) the Welch $t$-test with or without bootstrap calibration attains the type I error and produces similar levels of power with the former testing procedures, and d) the Wilcoxon-Mann-Whitney test produces inflated type I error while the computation of an exact p-value is not feasible in the presence of ties with discrete data. Further, an application to real gene expression data illustrates the computational high cost and thus the impracticality of the non parametric likelihoods. Overall, the Welch t-test, which is highly computationally efficient and readily interpretable, is shown to be the best method when testing equality of two population means., Accepted for publication in the Journal of Statistical Computation and Simulation

Purpose: To analyze the applicability of the Pediatric Evaluation of Disability Inventory (PEDI) to the Spanish population, and to assess the influence of demographic variables on the functional performance of the child. Method: The Spanish version of the PEDI was administered via interview representing a sample of 199 children without disability. The applicability of the PEDI was analyzed with the Welch t test and differences between the variables were analyzed using single-factor analysis of variance. Results: Significant differences in overall and domain-specific performance were found between Spanish and American samples. The Spanish sample's average score was lower than the American sample. Differences in performance within the Spanish sample were found by age, sex, and rural/urban living environment. Conclusions: The normative values of the PEDI should be applied with caution in the Spanish population until further data are available; however, the PEDI remains a useful instrument for monitoring functional change.

Background: Zeolite is a microporous aluminosilicate compound which has been successfully used in tissue engineering. The effects of Zeolite on the morphology and functions of pre-osteoblastic MG-63 cells as new bone enhancer material is still unclear. Methods: In this vitro experimental study, MTT and Alizarin red staining test were performed on six groups of MG-63 cells which differed in Zeolite (Z) concentration and the presence or absence of Alloplast extract (A). Group A: 0.1μg/mL Z+A, Group B: 0.1μg/mL Z without A, Group C: 0.2μg/mL Z+A, Group D: 0.2μg/mL Z without A, Group E: 0.3μg/mL Z+A, Group F: 0.3μg/mL Z without A. There were also three control groups as positive control, negative control, and Alloplast control based on each related test. The data were analyzed by SPSS 20 via one-way ANOVA and Welch test. (P

Urban trees are generally considered to be a public asset and are an important part of a city’s heritage. The aim of this work is to analyse the influence of season on the economic appraisal of various trees in Madrid. Photographs were taken of 43 individual tree specimens in summer and winter. The survey was designed to compare differences of opinion in the economic assessment of trees. The trees were assessed by eight valuation methods used worldwide. A total of 78 agroforestry engineering students answered a written survey, and the variables considered were: percentage of students who always evaluated the tree equally (%0), percentage of students who assigned more value to the summer photograph (%S), and percentage of students who assigned more value to the winter photograph (%W). The results were analysed by the statistical test of equal proportions and ANOVA to detect differences according to tree type (evergreen or deciduous), species, and other groupings made by the authors in previous works. W and S percentages are similar. The ANOVA analysis rejects the equality of percentages of S and W between groups. The Welch test rejects the equality of the percentage of S, W, and O between species.

The continued search for sustainable and eco-friendly materials has led to the integration of bio-fibers, such as flax fiber, as reinforcement in composite materials; however, a wide variation in their diameters and mechanical properties poses a considerable challenge for their incorporation in load bearing and structural bio-composite materials. In this paper, a rigorous experimental investigation was performed using two varieties of linseed flax from two growing locations to determine if the variations observed in ultimate tensile strength, Young’s modulus, failure strain and diameter could be attributed to the diameters of the stems that produced the fibers. Tests were performed in two different facilities and the results were compared and analyzed using Welch’s t-tests. Results showed that samples which differed by stem diameter had statistically significant positive correlation with fiber diameter and negative correlation with tensile strength. No correlations for tensile strength, Young’s modulus or fiber diameter were found in samples with the same stem diameter range that were grown in different locations or were of different varieties, that is the effect of location and variety is not statistically significant. Failure strain did not show any statistical significance with respect to differences in stem diameter and only showed one statistically significant result between both facilities for one of the two growing location comparisons.

BACKGROUND AND PURPOSE: Pretreatment diagnosis for the location of shunts and arterial feeders of spinal arteriovenous fistulas is crucial. This study aimed to evaluate the utility of subtracted CT angiography imaging by using nonrigid registration (R-CTA) in patients with spinal arteriovenous fistulas compared with conventional CTA imaging. MATERIALS AND METHODS: The records of 15 consecutive subjects (mean age, 65 years; 2 women) who had undergone CTA and digital subtraction angiography for clinically suspected spinal arteriovenous fistula were reviewed. From CTA images obtained at the arterial and late arterial phases, warped images of the late arterial phase were obtained by using nonrigid registration that was adjusted to the arterial phase images. R-CTA images were then obtained by subtracting the warped images from the arterial phase images. The accuracies of using nonrigid registration and conventional spinal CTA and the time required for detecting arterial feeders in spinal arteriovenous fistulas were analyzed for each patient with DSA results as a standard reference. The difference between R-CTA and conventional spinal CTA was assessed by the Welch test and the McNemar χ2 test. RESULTS: R-CTA had a higher accuracy compared with conventional spinal CTA (80% versus 47%, P = .025). The time for interpretation was reduced in R-CTA compared with conventional spinal CTA (45.1 versus 97.1 seconds, P = .002). CONCLUSIONS: Our subtracted CTA imaging by using nonrigid registration detects feeders of spinal arteriovenous fistulas more accurately and quickly than conventional CTA.

Methods to detect covert timing channels (CTCs) can be categorized into three broad classes: shape tests which include the Kolmogorov-Smirnov (KS) test, entropy tests which include first order entropy test, corrected conditional entropy (CCE) test, and Kullback-Leibler (KL) divergence test, and regularity tests. This paper contributes towards understanding and advancing the state-of-the-art of CTC detection methods. First, we present a detailed analysis of the performance of the well-known tests that are used to detect three main types of CTCs, namely, JitterBug, model-based CTC (MB-CTC) and time-replay CTC (TR-CTC). The performance analysis is carried out in an enterprise-like setting, employing large traffic traces. The detection methods are compared with respect to their applicability, computational complexity, and the classification rates for the three types of CTCs. In addition to evaluating the existing methods, we propose a new shape test based on the Welch's t-test and compare its performance with existing detection methods. We show that the classification rate of Welch's t-test is at least at par with other existing detection methods while having a relatively lower computational cost. The results also show that the Welch's t-test outperforms the CCE test in detecting JitterBug, while the CCE test has a better performance in detecting the TR-CTC. Furthermore, both tests perform comparably on the MB-CTC. Finally, we study the feasibility of using a multi-feature SVM classifier to increase the classification rate. We show that by combining the Welch's t-test we are able to increase the classification rate of MB-CTCs from 0.67 (using a single regularity measure) to 0.94.

An alternative to the Satterswaite-Welch degrees of freedom (df) is developed in this paper based on unbiased estimating equations. The method enables us to evaluate the impact of sample variation due to using estimated df instead of the true df by computer intensive method. It is shown by simulation that the alternative df is close to the Welch df and the method developed could be also used for evaluating the impact of sample variation due to using estimated df in the Welch test.

In order to objectively evaluate the systematic differences in the area of annual disaster relief before and after the scientific implementation of artificial flood control in the Akesu area of Xinjiang, the effect of artificial flood control in the area was analyzed. This paper uses the data of the annual disaster area of the Akesu area from 1978 to 2013, and starts the year of artificial flood control operation in 1996 as a science. Using the statistical methods such as sequence test, unpaired rank sum test and Welch test, artificial prevention of science The systematic differences in the annual disaster area of each 18a before and after the operation were analyzed. The results show that the hail disasters in the Akesu area are significantly reduced after the artificial anti-mite operation. The non-parametric unpaired rank sum test has a significance level of 0.05, the parametric Welch test has a significance level of 0.01, and the average annual disaster area is reduced by 15063 hm2. The reduction rate was 43.14%. Combined with agricultural economic data, the annual average reduction of disaster relief losses is 281.09 million yuan, the annual input-output ratio is 1:6, and the statistical significance level reaches 0.1. Therefore, after the scientific implementation of artificial flood control operations in the Akesu area, the hail disaster losses are significantly reduced, and the social and economic benefits of disaster reduction are significant.

Purpose: Early diagnosis or detection of Alzheimer's disease (AD) from the normal elder control (NC) is very important. However, the computer-aided diagnosis (CAD) was not widely used, and the classification performance did not reach the standard of practical use. We proposed a novel CAD system for MR brain images based on eigenbrains and machine learning with two goals: accurate detection of both AD subjects and AD-related brain regions. Method: First, we used maximum inter-class variance (ICV) to select key slices from 3D volumetric data. Second, we generated an eigenbrain set for each subject. Third, the most important eigenbrain (MIE) was obtained by Welch's t-test (WTT). Finally, kernel support-vector-machines with different kernels that were trained by particle swarm optimization, were used to make an accurate prediction of AD subjects. Coefficients of MIE with values higher than 0.98 quantile were highlighted to obtain the discriminant regions that distinguish AD from NC. Results: The experiments showed that the proposed method can predict AD subjects with a competitive performance with existing methods, especially the accuracy of the polynomial kernel (92.36 ± 0.94) was better than the linear kernel of 91.47 ± 1.02 and the radial basis function (RBF) kernel of 86.71 ± 1.93. The proposed eigenbrain-based CAD system detected 30 AD-related brain regions (Anterior Cingulate, Caudate Nucleus, Cerebellum, Cingulate Gyrus, Claustrum, Inferior Frontal Gyrus, Inferior Parietal Lobule, Insula, Lateral Ventricle, Lentiform Nucleus, Lingual Gyrus, Medial Frontal Gyrus, Middle Frontal Gyrus, Middle Occipital Gyrus, Middle Temporal Gyrus, Paracentral Lobule, Parahippocampal Gyrus, Postcentral Gyrus, Posterial Cingulate, Precentral Gyrus, Precuneus, Subcallosal Gyrus, Sub-Gyral, Superior Frontal Gyrus, Superior Parietal Lobule, Superior Temporal Gyrus, Supramarginal Gyrus, Thalamus, Transverse Temporal Gyrus, and Uncus). The results were coherent with existing literatures. Conclusion: The eigenbrain method was effective in AD subject prediction and discriminant brain-region detection in MRI scanning.