Search

The recent emergence of COVID-19 has drawn attention to the various methods of disease control. Since no proper treatment is available till date and the vaccination is restricted to certain age groups, also vaccine efficacy is still under progress, the emphasis has been given to the method of isolation and quarantine. This control is induced by tracing the contacts of the infectious individuals, putting them to the quarantine class and based on their symptoms, classifying them either as the susceptible or sick individuals and moving the sick individuals to the isolated class. To track the current pandemic situation of COVID-19 in India, we consider an extended Susceptible-Exposed-Quarantine-Infected-Isolated-Recovered (SEQ1IQ2R) compartmental model along with calculating its control reproductive number Rc. The disease can be kept in control if the value of Rc remains below one. This "threshold" value of Rc is used to optimize the period of quarantine, and isolation and have been calculated in order to eradicate the disease. The sensitivity analysis of Rc with respect to the quarantine and isolation period has also been done. Partial rank correlation coefficient method is applied to identify the most significant parameters involved in Rc. Based on the observed data, 7-days moving average curves are plotted for prelockdown, lockdown and unlock 1 phases. Following the trend of the curves for the infection, a generalized exponential function is used to estimate the data, and corresponding 95% confidence intervals are simulated to estimate the parameters. The effect of control measures such as quarantine and isolation are discussed. Following various mathematical and statistical tools, we systematically explore the impact of lockdown strategy in order to control the recent outbreak of COVID-19 transmission in India. [ABSTRACT FROM AUTHOR]

One method for modeling geometric variations in hyperstatic (i.e. overconstrained) systems is to use sets of constraints. Different models have been developed in this way, e.g. domains, T-maps, and polytopes. In general, if the intersection of the contact constraints between two parts potentially in contact is nonempty, the parts can be assembled without interference, and their relative positions determined. In this study, the polytope method is used with a statistical approach to define the behavior of an assembly. In the first part, geometric variations including form deviations of individual parts are defined. The relations between these variations resulting from the architecture of a mechanism are then defined. In the second part, contact constraints are introduced and the general method to conform the constraints into double description polytopes is presented. The general process to simulate the compliance of the mechanism with respect to functional conditions is described. A failure rate is obtained for a simulated population of manufactured parts using the Monte Carlo method. In the third part, an application to a flange is described, an example from an industrial case study. We show how to take advantage of double description of polytopes when simulating the assembly and the misalignment of the two parts that make up the flange. Finally, we present our conclusions and prospects for future studies. [ABSTRACT FROM AUTHOR]

Tolerance analysis of an assembly is an important issue for mechanical design. Among various tolerance analysis methods, statistical analysis is the most commonly employed method. However, the conventional statistical tolerance method is often based on the normal distribution. It fails to predict the resultant tolerance of an assembly of parts with non-normal distributions. In this paper, a novel method based on statistical moments is proposed. Tolerance distributions of parts are first transferred into statistical moments that are then used for computing tolerance stack-up. The computed moments, particularly the variance, the skewness and the kurtosis, are then mapped back to probability distributions in order to calculate the resultant tolerance of the assembly. The proposed method can be used to analyse the resultant tolerance specification for non-normal distributions with different skewness and kurtosis. Simulated results showed that tail coefficients of different distributions with the same kurtosis are close to each other for normalised probabilities between −3 and 3. That is, the tail coefficients of a statistical distribution can be predicted by the coefficients of skewness and kurtosis. Two examples are illustrated in the paper to demonstrate the proposed method. The predicted resultant tolerances of the two examples are only 0.5% and 1.5% differences compared with that by the Monte Carlo simulation for 1,000,000 samples. The proposed method is much faster in computation with higher accuracy than conventional statistical tolerance methods. The merit of the proposed method is that the computation is fast and comparatively accurate for both symmetrical and unsymmetrical distributions, particularly when the required probability is between ±2σ and ±3σ. [ABSTRACT FROM PUBLISHER]

The experimental design technique in the literature, which has been limited only to normally distributed random variables, is extended to handle non-normal cases. It is easy to implement and provides good results for the moments of system response functions compared with other traditional methods. It is based on the three-level Taguchi method, and optimum levels and weights to handle non-normal distributions are derived. A systematic procedure for tolerance analysis is then proposed by using the Pearson system. Numerical results for non-linear examples are shown to be very accurate in comparison with those from Monte Carlo simulations and the first-order reliability method. [ABSTRACT FROM AUTHOR]

The paper presents a simple approximation technique for statistical tolerance analysis, namely, the allocation of component tolerances based on a known assembly tolerance. The technique utilizes a discretized, multivariate kernel density estimate and a simple transformation to approximate the probability distribution of the overall assembly characteristic. The data-driven approach is suitable for real-world settings in which components are randomly selected from their respective manufacturing processes to form mechanical assemblies. Demonstrated is the numerical approach in two dimensions for two distinct cases: first, when component characteristics are non-normal, independent random variables, and second, when they are highly correlated, normal random variables. The results are promising in initial test problems. [ABSTRACT FROM AUTHOR]

In general, there are two purposes in identifying dimensional chains for a part's process plan: determining the nominal dimensions and allocating proper tolerances to these dimensions for manufacturing operations. This paper proposes an algebraic approach for dimensional chain identification based on the tolerance charting technique. Before the new approach is presented, the digraphic method is outlined in order to introduce the concept of the reverse dimensional chain and to express the relationship between the reverse and the forward dimensional chains. However, the algebraic approach presented in this paper does not require the generation of any graphs or trees. It identifies the reverse dimensions by use of the original tolerance chart. The forward dimensional chains are obtained from the reverse dimensional chains by use of the relationship between the reverse and the forward dimensional chains. The reverse dimensional chains can be used to determine the nominal dimensions directly while the forward dimensional chains are necessary to allocate the tolerances for manufacturing. [ABSTRACT FROM AUTHOR]

In this paper we study several related problems of finding optimal interval and circular-arc covering. We present solutions to the maximum k-interval (k-circular-arc) coverage problems, in which we want to cover maximum weight by selecting k intervals (circular-arcs) out of a given set of intervals (circular-arcs), respectively, the weighted interval covering problem, in which we want to cover maximum weight by placing k intervals with a given length, and the k-centers problem. The general sets version of the discussed problems, namely the general measure k-centers problem and the maximum covering problem for sets are known to be NP-hard. However, for the one dimensional restrictions studied here, and even for circular-arc graphs, we present efficient, polynomial time, algorithms that solve these problems. Our results for the maximum k-interval and k-circular-arc covering problems hold for any right continuous positive measure on R. [ABSTRACT FROM AUTHOR]

The differential pattern and characteristics of completeness in adverse event (AE) reports generated by hospitals/clinics, pharmacies, consumer and pharmaceutical companies remain unknown. Thus, we identified the characteristics of complete AE reports, compared with those of incomplete AE reports, using a completeness score. We used Korea Institute of Drug Safety and Risk Management-Korea Adverse Event Reporting System Database (KIDS-KD) between January 1, 2016 and December 31, 2016. The completeness score was determined out of a total of 100 points, based on the presence of information on temporal relationships, age and sex of patients, AE progress, name of reported medication, reporting group by profession, causality assessment, and informational text. AE reports were organized into four groups based on affiliation: hospitals/clinics, pharmacies, consumers, and pharmaceutical companies. Affiliations that had median completeness scores greater than 80 points were classified as ‘well-documented’ and these reports were further analyzed by logistic regression to estimate the adjusted odds ratios and 95% confidence intervals. We examined 228,848 individual reports and 735,745 drug-AE combinations. The median values of the completeness scores were the highest for hospitals/clinics (95 points), followed by those for consumers (85), pharmacies (75), and manufacturers (72). Reports with causality assessment of ‘certain’, ‘probable’, or ‘possible’ were more likely to be ‘well-documented’ than reports that had causality assessments of ‘unlikely’. Serious reports of AEs were positively associated with ‘well-documented’ reports and negatively associated with hospitals/clinics. [ABSTRACT FROM AUTHOR]

Statistical tolerance intervals for discrete distributions are widely employed for assessing the magnitude of discrete characteristics of interest in applications like quality control, environmental monitoring, and the validation of medical devices. For such data problems, characterizing extreme counts or outliers is also of considerable interest. These applications typically use traditional discrete distributions, like the Poisson, binomial, and negative binomial. The discrete Pareto distribution is an alternative yet flexible model for count data that are heavily right‐skewed. Our contribution is the development of statistical tolerance limits for the discrete Pareto distribution as a strategy for characterizing the extremeness of observed counts in the tail. We discuss the coverage probabilities of our procedure in the broader context of known coverage issues for statistical intervals for discrete distributions. We address this issue by applying a bootstrap calibration to the confidence level of the asymptotic confidence interval for the discrete Pareto distribution's parameter. We illustrate our procedure on a dataset involving cyst formation in mice kidneys. [ABSTRACT FROM AUTHOR]

Over-constrained assembly of rigid parts is widely adopted in aircraft assembly to yield higher stiffness and accuracy of assembly. Unfortunately, the quantitative tolerance analysis of over-constrained assembly is challenging, subject to the coupling effect of geometrical and physical factors. Especially, gravity will affect the geometrical gaps in mechanical joints between different parts, and thus influence the deviations of assembled product. In the existing studies, the influence of gravity is not considered in the tolerance analysis of over-constrained assembly. This paper proposes a novel tolerance analysis method for over-constrained assembly of rigid parts, considering the gravity influence. This method is applied to a typical over-constrained assembly with constraints of multiple planar hole-pin-hole pairs. This type of constraints is non-linear, which makes the tolerance analysis more challenging. Firstly, the deviation propagation analysis of an over-constrained assembly is conducted. The feasibility of assembly is predicted, and for a feasible assembly, the assembly deviations are determined with the principle of minimum potential energy. Then, the statistical tolerance analysis is performed. The probabilities of assembly feasibility and quality feasibility are computed, and the distribution of assembly deviations is estimated. Two case studies are presented to show the applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Statistical tolerancing was first proposed by Shewhart (Economic Control of Quality of Manufactured Product, (1931) reprinted 1980 by ASQC), in spite of this long history, its use remains moderate. One of the probable reasons for this low utilization is undoubtedly the difficulty for designers to anticipate the risks of this approach. The arithmetic tolerance (worst case) allows a simple interpretation: conformity is defined by the presence of the characteristic in an interval. Statistical tolerancing is more complex in its definition. An interval is not sufficient to define the conformance. To justify the statistical tolerancing formula used by designers, a tolerance interval should be interpreted as the interval where most of the parts produced should probably be located. This tolerance is justified by considering a conformity criterion of the parts guaranteeing low offsets on the latter characteristics. Unlike traditional arithmetic tolerancing, statistical tolerancing requires a sustained exchange of information between design and manufacture to be used safely. This paper proposes a formal definition of the conformity, which we apply successively to the quadratic and arithmetic tolerancing. We introduce a concept of concavity, which helps us to demonstrate the link between tolerancing approach and conformity. We use this concept to demonstrate the various acceptable propositions of statistical tolerancing (in the space decentring, dispersion). [ABSTRACT FROM AUTHOR]

Letter displays are often used to report results of all pairwise comparisons among treatment means in comparative experiments. In captions to tables and charts using such letter displays, it is crucial to explain properly what the letters mean. In this paper I explain what the letters mean and how this meaning can be succinctly conveyed in a single sentence without ambiguity. This is contrasted to counter-examples commonly found in publications. [ABSTRACT FROM AUTHOR]

Objective To determine whether patients with lumbosacral (LS) radiculopathy and peripheral polyneuropathy (PPNP) exhibit sudomotor abnormalities and whether SUDOSCAN (Impeto Medical, Paris, France) can complement nerve conduction study (NCS) and electromyography (EMG). Methods Outpatients with lower extremity dysesthesia underwent electrophysiologic studies and SUDOSCAN. They were classified as normal (group A), LS radiculopathy (group B), or PPNP (group C). Pain severity was measured by the Michigan Neuropathy Screening Instrument (MNSI) and visual analogue scale (VAS). Demographic features, electrochemical skin conductance (ESC) values on hands and feet, and SUDOSCAN-risk scores were analyzed. Results There were no statistical differences in MNSI and VAS among the three groups. Feet-ESC and hands-ESC values in group C were lower than group A and B. SUDOSCAN-risk score in group B and C was higher than group A. With a cut-off at 48 microSiemens of feet-ESC, PPNP was detected with 57.1% sensitivity and 94.2% specificity (area under the curve [AUC]=0.780; 95% confidence interval [CI], 0646-0.915). With a SUDOSCAN-risk score cut-off at 29%, NCS and EMG abnormalities related to LS radiculopathy and PPNP were detected with 64.1% sensitivity and 84.2% specificity (AUC=0.750; 95% CI, 0.674-0.886). Conclusion SUDOSCAN can discriminate outpatients with abnormal electrophysiological findings and sudomotor dysfunction. This technology may be a complementary tool to NCS and EMG in outpatients with lower extremity dysesthesia. [ABSTRACT FROM AUTHOR]

Error bars are useful to understand data and their interrelations. Here, it is shown that confidence intervals of the mean (CIMs) can be adjusted based on whether the objective is to highlight differences between measures or not and based on the experimental design (within- or between-group designs). Confidence intervals (CIs) can also be adjusted to take into account the sampling mechanisms and the population size (if not infinite). Names are proposed to distinguish the various types of CIs and the assumptions underlying them, and how to assess their validity is explained. The various CIs presented here are easily obtained from a succession of multiplicative adjustments to the basic (unadjusted) CI width. All summary results should present a measure of precision, such as CIs, as this information is complementary to effect sizes. [ABSTRACT FROM AUTHOR]

The problem of identification of a mathematical model of the strength of welded joints by measurements is investigated using data obtained in measurements of the parameters of resistance spot welding in the three-factorial measurement experiment. [ABSTRACT FROM AUTHOR]

For the problem of small samples estimation in engineering practice, a new method of the grey confidence interval estimation for small samples based on numerical characteristics is studied. According to the degree of aggregation of small sample data, the concept of the distance standard deviation, which is an important numerical characteristic, is defined. At the same time, the concept of sample dispersion degree is proposed to describe the degree of dispersion between different samples. On the basis of the new definition of grey weight, the grey point estimation is proposed. Then, the grey distance approach improved by distance standard deviation and sample distance, are put forward with their numerical characteristic. In addition, the accurate grey bilateral and unilateral confidence intervals are introduced under the new grey distance approach. Finally, several examples are used to demonstrate the rationality and effectiveness of the methods proposed above. The comparative results show that the proposed methods have higher precision in reflecting the characteristics of data density. [ABSTRACT FROM AUTHOR]

In this paper we consider Pareto-Rayleigh distribution as an example of a Transformed-Transformer family of distributions defined by Alzaatreh et al. (2013b). We construct confidence intervals (CIs) and tolerance intervals (TIs) using generalized variable approach due to Weerahandi (1993) by using maximum likelihood estimator and modified maximum likelihood estimator of the scale parameter. Performance of both the intervals is studied using simulation and compared with the existing ones to exhibit superiority of the proposed intervals. Proposed confidence intervals and tolerance intervals are illustrated through real life data. [ABSTRACT FROM AUTHOR]

In this study, we consider the construction of the confidence interval for the population proportion while using group testing with misclassification. We propose two confidence intervals based on Cornish-Fisher expansion and a modified Wilson's interval based on a newly developed estimator. We investigate the performance of these intervals extensively and also apply the methods to real datasets. Our newly derived methods have competitive performance compared with existing methods. [ABSTRACT FROM AUTHOR]

Hypothesis testing procedures where equality of means is assessed at a prespecified level based on the (non-)overlap of confidence intervals are discussed. Assessing statistical significance via the (non-)overlap of two confidence intervals with an appropriate confidence level provides a simple and effective way of visually understanding statistical results. This article extends previous approaches by considering range-preserving confidence intervals where the values in such intervals are in the allowable range of the parameter of interest. To obtain reliable procedures, appropriate effective degrees of freedom are suggested by considering the Welch-Satterthwaite equation for both independent two-sample and paired-sample cases. The proposed procedures also allow users to express results in terms of commonly used scale-free effect sizes, which are highly useful for interpreting parameters of interest. Simulation results suggest that the proposed procedures may be robust to unequal or small sample sizes, nonnormal distributions, heterogeneous variances, and various degrees of correlation. A real-life application from a study in cognitive psychology illustrates the effectiveness of the proposed procedures. [ABSTRACT FROM PUBLISHER]

It is presented in this study a method by calculation of the dimensional chains which take into account by dimensional repartitions of the component elements of the dimensional chain: production cost is decreasing and the possibility of calculation of the dimensional chains with the help of computer appears. In this paper it emphasizes the factor of increases and the factor of reduction, factors influencing tolerance values of the components elements of a chain of sizes. The factor of increase and the factor of reduction depends on the type dimensional distribution [ABSTRACT FROM AUTHOR]

Background: A growing number of rapid Helicobacter pylori antibody tests are commercially available now, however, some of these tests are often used without sufficient evaluation. The aim of this study was to evaluate the performance of a commercially available rapid whole-blood immunoassay (gabControl® H. pylori; gabmed GmbH, Köln, Germany), for the qualitative detection of IgG antibodies against H. pylori with the 13C-urea breath test (13C-UBT) serving as a reference method. Methods: A total of 108 consecutive outpatients, who were referred for 13C-UBT by general practitioners and specialists, were also tested for H. pylori infection by the gabControl® H. pylori immunoassay. The clinical performance of this rapid whole-blood test was evaluated by determining the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) compared to the 13C-UBT. The agreement between the two tests was calculated using Cohen's Kappa (κ) with 95 % confidence intervals (CI). Results: The agreement between the gabControl® H. pylori assay and the 13C-UBT was 0.62 [95 % confidence intervals (CIs) 0.47-0.76; P < 0.001]. With the 13C-UBT serving as the non-invasive gold standard method of H. pylori diagnosis, the gabControl® H. pylori assay demonstrated a sensitivity and specificity of 91.4 and 76.7 %, respectively, with a PPV of 65.3 % and a NPV of 94.9 %. Seventeen (15.7 %) individuals with a positive H. pylori anamnesis showed a negative 13C-UBT and were typed positive by the gabControl® H. pylori assay. Of these, 13 (76.5 %) and 3 individuals (17.6 %) had completed one and two eradication therapies, respectively. Conclusions: The gabControl® H. pylori immunoassay is a rapid and easy to use first line screening tool for H. pylori IgG antibody detection in daily clinical practice. However, this assay should not be used for confirmation of the successful H. pylori eradication after antibiotic treatment. [ABSTRACT FROM AUTHOR]

Background: Group A streptococci (GAS) are the most common bacterial cause of acute pharyngitis and account for 15-30 % of cases of acute pharyngitis in children and 5-10 % of cases in adults. In this study, a real-time quantitative PCR (qPCR) based GAS detection assay in pharyngeal swab specimens was developed. Methods: The qPCR assay was compared with the gold standard bacterial culture and a rapid antigen detection test (RADT) to evaluate its clinical performance in 687 patients. The analytical sensitivity of the assay was 240 cfu/swab. Forty-five different potential cross-reacting organisms did not react with the test. Four different laboratories for the reproducibility studies were in 100 % (60/60) agreement for the contrived GAS positive and negative swab samples. Results: The relative sensitivities of the RADT and the qPCR test were 55.9 and 100 %; and the relative specificities were 100 and 96.3 %, respectively. Duration of the total assay for 24 samples including pre-analytical processing and analysis changed between 42 and 55 min depending on the type of qPCR instrument used. A simple DNA extraction method and a low qPCR volume made the developed assay an economical alternative for the GAS detection. Conclusion: We showed that the developed qPCR test is rapid, cheap, sensitive and specific and therefore can be used to replace both antigen detection and culture for diagnosis of acute GAS pharyngitis. [ABSTRACT FROM AUTHOR]

We consider the problem of simultaneously estimating Poisson rate differences via applications of the Hsu and Berger stepwise confidence interval method (termed HBM), where comparisons to a common reference group are performed. We discuss continuity-corrected confidence intervals (CIs) and investigate the HBM performance with a moment-based CI, and uncorrected and corrected for continuity Wald and Pooled confidence intervals (CIs). Using simulations, we compare nine individual CIs in terms of coverage probability and the HBM with nine intervals in terms of family-wise error rate (FWER) and overall and local power. The simulations show that these statistical properties depend highly on parameter settings. [ABSTRACT FROM AUTHOR]

Two-sided asymptotic confidence intervals for an unknown proportion p have been the subject of a great deal of literature. Surprisingly, there are very few papers devoted, like this article, to the case of one tail, despite its great importance in practice and the fact that its behavior is usually different from that of the case with two tails. This paper evaluates 47 methods and concludes that (1) the optimal method is the classic Wilson method with a correction for continuity and (2) a simpler option, almost as good as the first, is the new adjusted Wald method (Wald's classic method applied to the data increased in the values proposed by Borkowf: adding a single imaginary failure or success). [ABSTRACT FROM AUTHOR]

A 95% confidence interval (CI) of the mean is a range with an upper and lower number calculated from a sample. Because the true population mean is unknown, this range describes possible values that the mean could be. If multiple samples were drawn from the same population and a 95% CI calculated for each sample, we would expect the population mean to be found within 95% of these CIs. CIs are sensitive to variability in the population (spread of values) and sample size. When used to compare the means of two or more treatment groups, a CI shows the magnitude of a difference between groups. This is helpful in understanding both the statistical significance and the clinical significance of a treatment. In this article we describe the basic principles of CIs and their interpretation. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to estimate the process capability for a profile geometric tolerance as defined by the ASME YI4.5 standard. The novelty of the method is that it uses the known process capability of a given geometry to predict, using the order statistics theorem, new capabilities for different geometries of higher or lower complexity. By considering the geometrical complexity of mechanical parts, a manufacturing process may be capable (e.g., Cpk > 1.5) for parts with simple geometiy and incapable (e.g., Cpk < I) for parts with complex geometry. In the proposed model, the process capability becomes a mathematical function of both the statistical behavior of the process (e.g., expectation and variance) and the geometric complexity of manufactured surfaces. Three experimental case studies are presented to illustrate the usefulness and the validity of the developed model. [ABSTRACT FROM AUTHOR]

Background: Clustering commonly affects the uncertainty of parameter estimates in epidemiological studies. Cluster-robust variance estimates (CRVE) are used to construct confidence intervals that account for single-level clustering, and are easily implemented in standard software. When data are clustered at more than one level (e.g. village and household) the level for the CRVE must be chosen. CRVE are consistent when used at the higher level of clustering (village), but since there are fewer clusters at the higher level, and consistency is an asymptotic property, there may be circumstances under which coverage is better from lower- rather than higher-level CRVE. Here we assess the relative importance of adjusting for clustering at the higher and lower level in a logistic regression model.Methods: We performed a simulation study in which the coverage of 95 % confidence intervals was compared between adjustments at the higher and lower levels.Results: Confidence intervals adjusted for the higher level of clustering had coverage close to 95 %, even when there were few clusters, provided that the intra-cluster correlation of the predictor was less than 0.5 for models with a single predictor and less than 0.2 for models with multiple predictors.Conclusions: When there are multiple levels of clustering it is generally preferable to use confidence intervals that account for the highest level of clustering. This only fails if there are few clusters at this level and the intra-cluster correlation of the predictor is high. [ABSTRACT FROM AUTHOR]

Background: Implementing International Organization for Standardization definitions of limit of blank and limit of detection requires precision estimates from specimens devoid of analyte (blank specimens) and also from specimens located close to zero. Calculations are straightforward if errors are constant over the relevant concentration range but estimation of the relationship between variability and concentration (variance function) is necessary in the general case when errors are not constant. This study investigated the efficacy of incorporating the variance function into estimation of limit of blank, limit of detection and their confidence intervals.Methods: Simulated data, designed to encompass the range of properties that would typically be observed in practice, consisted of four distinct relationships between variance and concentration, in combination with large and small variances and three concentration ranges. Four methods of estimating limit of blank were evaluated together with the accuracy of variance function derived estimates of limit of detection and the accuracy of symmetrical 95% confidence intervals constructed from limit of blank and limit of detection constituent variables.Results: Most limit of blank estimates and all limit of detection estimates showed systematic negative bias but, provided the data concentration range is not too small, the biases were consistently <1% with confidence interval coverages ranging from 92% to 95%. Estimating limit of blank by extrapolating the variance function to zero lost little in comparison with methods based on blank specimen data.Conclusions: The variance function provides a convenient and reliable way of analyzing data from experiments evaluating detection capability and, provided certain assumptions are tenable, of estimating limit of blank and limit of detection as part of routine internal quality control. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the risk of site-specific and overall malignancies after SLE and explore the potential influencing factors. Methods: We searched electronic databases for articles that assessed the risk of malignancies after SLE through February 2015. We extracted the incidence rates (IRs) and corresponding 95 % confidence intervals (CIs). We used random effects models to calculate the pooled IRs and assessed the impact of study designs, region, gender, age and duration of follow-up. Results: Eighteen studies were included, giving a pooled IR of 1.44 (95 % CI 1.23-1.69). Europeans, Americans and Asians showed a IR of 1.56 (95 % CI 1.07-2.28), 1.18 (95 % CI 1.01-1.39) and 1.62 (95 % CI 1.38-1.89), respectively. Males and females (eight studies) demonstrated a IR of 1.34 (95 % CI 1.07-1.67) and 1.51 (95 % CI 1.20-1.90), respectively. Prospective and retrospective studies showed a IR of 1.55 (95 % CI 0.97-2.47) and 1.44 (95 % CI 1.21-1.73), respectively. An increment of 10 years of age conferred a decrease in IR of 0.6. An increment of 5 years of SLE duration conferred a decrease in IR of 2.5. An increased IR of malignancies was observed in NHL, vagina/vulva, hematology, head/neck, leukemia, thyroid, liver/gallbladder, kidney, anal, cervix, esophagus, lung and pancreas. A decreased IR of malignancies was observed in ovary and colon/rectum. Conclusions: SLE patients had an increased risk of developing overall malignancies, particularly among Asians and females. Age and SLE duration are inversely associated with the risk of overall malignancies. SLE patients showed a different role in the onset of various site-specific malignancies. [ABSTRACT FROM AUTHOR]

Tolerance analysis is an analytical tool for the estimation of accumulating effects of the individual part tolerances on the functional requirements of a mechanical assembly. This article presents a comprehensive feature-based method for tolerance analysis of mechanical assemblies with both dimensional and geometric tolerances. In this method, dimensional and geometric tolerance zones are described by the combination of fuzzy modelling and small degrees of freedom (SDOF) concept. In this model, the uncertainty in dimensions and geometric form of features is mathematically described using fuzzy modelling, and the kinematic effects of tolerances in assemblies are expressed by SDOF concept. In the proposed method, complicated GD&T concepts such as various material modifiers (maximum material condition, least material condition and regardless of feature size), envelope requirement, bonus tolerances and Rule No. 1 (Taylor principle) in several conditions are accurately modelled. Compatible with the proposed model, a procedure for modified worst case and statistical tolerance accumulation analysis is introduced. An algorithm is laid out that describes the steps and the procedure of tolerance analysis. The application of this method is demonstrated through an example, and the results are compared with experimental results. [ABSTRACT FROM AUTHOR]

Reliable streamflow forecasts are very significant for reservoir operation and hydropower generation. But for monthly streamflow forecasting, the forecasting result is unreliable and it is hard to be utilized, although it has a certain reference value for long-term hydro generation scheduling. Current researches mainly focus on deterministic scheduling, and few of them consider the uncertainties. So this paper considers the forecasting error which exists in monthly streamflow forecasting and proposes a new long-term hydro generation scheduling method called forecasting dispatching chart for Xiluodu and Xiangjiaba cascade hydro plants. First, in order to consider the uncertainties of inflow, Monte Carlo simulation is employed to generate streamflow data according to the forecasting value and error distribution curves. Then the large amount of data obtained by Monte Carlo simulation is used as inputs for long-term hydro generation scheduling model. Because of the large amount of streamflow data, the computation speed of conventional algorithm cannot meet the demand. So an improved parallel progressive optimality algorithm is proposed to solve the long-term hydro generation scheduling problem and a series of solutions are obtained. These solutions constitute an interval set, unlike the unique solution in the traditional deterministic long-term hydro generation scheduling. At last, the confidence intervals of the solutions are calculated and forecasting dispatching chart is proposed as a new method for long-term hydro generation scheduling. A set of rules are proposed corresponding to forecasting dispatching chart. The chart is tested for practical operations and achieves good performance. [ABSTRACT FROM AUTHOR]

The objective of this paper was to propose TestSTAT confidence interval estimation for a one parameter exponential distribution. Evaluation of the efficiency for this estimation was proved via theorems and a simulation study was conducted to compare the coverage probabilities and expected lengths of the three confidence intervals (TestSTAT, Exact and Asymptotic confidence intervals). The results showed that the TestSTAT confidence interval which is derived in this paper uses the same formula as for the Exact confidence interval which is widely used. Additionally, the expected length of the TestSTAT confidence interval is shorter than that of the Asymptotic confidence interval for a small sample size and all levels of the parameter and confidence coefficient. Furthermore, the three confidence interval estimations get systematically closer to the nominal level for all levels of the sample size and the parameter. In addition, the efficiencies of the three confidence interval estimations seem to be no different for a large sample size and all levels of the parameter and confidence coefficient. [ABSTRACT FROM AUTHOR]

Aim We investigated whether moxifloxacin-induced QTc prolongations in Japanese and Caucasian healthy male volunteers were significantly different. Methods A two period, randomized, crossover, ICH-E14-compliant thorough QT (TQT) study compared placebo-corrected changes in QTc interval from baseline (ΔΔQTcF) and concentration-effect relationships following administration of placebo and 400 mg moxifloxacin to 40 healthy male volunteers from each ethnic population. The point estimates of ΔΔQTcF for each population, and the difference between the two, were calculated at a geometric mean Cmax of moxifloxacin using a linear mixed effects model. The concentration-effect slopes of the two populations were also compared. Equivalence was concluded if the two-sided 90% confidence interval of the difference in ΔΔQTcF was contained within −5 ms to +5 ms limits and the ratio of the slopes was between 0.5 and 2. Results There were no statistically significant differences between the two populations studied, Japanese vs. Caucasians, respectively, for moxifloxacin Cmax (3.27 ± 0.6 vs. 2.98 ± 0.7 µg ml-1), ΔΔQTcF (9.63 ± 1.15 vs. 11.46 ± 1.19 ms at Cmax of 3.07 µg ml-1) and concentration-response slopes (2.58 ± 0.62 vs. 2.34 ± 0.64 ms per µg ml-1). The difference in the two ΔΔQTcF of −1.8 (90% CI −4.6, 0.9) and the ratio of the two slopes (1.1; 90% CI 0.63, 1.82) were within pre-specified equivalence limits. Conclusions Moxifloxacin-induced QTc prolongations did not differ significantly between the Japanese and Caucasian subjects. However, before our findings are more widely generalized, further studies in other populations and with other QT-prolonging drugs are needed to clarify whether inter-ethnic differences in QT sensitivity exist and whether ethnicity of the study population may affect the outcome of a TQT study. [ABSTRACT FROM AUTHOR]

Even elementary statistical problems may give rise to a deeper and broader discussion of issues in probability and statistics. The construction of an approximate confidence interval for a Poisson mean turns out to be such a case. The simple standard two-sided Wald confidence interval by normal approximation is discussed and compared with the score interval. The discussion is partly in the form of an imaginary dialog between a teacher and a student, where the latter is supposed to have studied mathematical statistics for at least one semester. [ABSTRACT FROM AUTHOR]

The construction of regions with assigned probabilitypand minimum geometric measure has theoretical and practical interests, such as the construction of tolerance regions. Following Azzalini (2001) and exploiting the normal approximation of the extended skew-normal distribution when some of its parameters go to infinity, we discuss an approach for the construction of regions with assigned probabilitypfor the bivariate extended skew-normal distribution. [ABSTRACT FROM PUBLISHER]

In this paper, we consider tolerances induced by irredundant coverings. Each tolerance R on U determines a quasiorder ≤R by setting x ≤R y if and only if R(x) &subseteq; R(y). We prove that for a tolerance R induced by a covering H of U, the covering H is irredundant if and only if the quasiordered set (U,≤R) is bounded by minimal elements and the tolerance R coincides with the product &nvge;R º ≤R. We also show that in such a case H = {&ShortUpArrow;m | m is minimal in (U,≤R)}, and for each minimal m, we have R(m) = &ShortUpArrow;m. Additionally, this irredundant covering H inducing R consists of some blocks of the tolerance R. We give necessary and sufficient conditions under which H and the set of R-blocks coincide. These results are established by applying the notion of Helly numbers of quasiordered sets. [ABSTRACT FROM AUTHOR]

Background: Exposure to particulate matter (PM) is generally associated with elevated risk of cardiovascular morbidity and mortality. Elderly and obese subjects may be particularly susceptible, although short-term effects are poorly described. Methods: Sixty healthy subjects (25 males, 35 females, age 55 to 83 years, body mass index > 25 kg/m2) were included in a cross-over study with 5 hours of exposure to particle- or sham-filtered air from a busy street using an exposure-chamber. The sham- versus particle-filtered air had average particle number concentrations of ~23.000 versus ~1800/cm3 and PM2.5 levels of 24 versus 3μg/m3, respectively. The PM contained similar fractions of elemental and black carbon (~20-25%) in both exposure scenarios. Reactive hyperemia and nitroglycerin-induced vasodilation in finger arteries and heart rate variability (HRV) measured within 1 h after exposure were primary outcomes. Potential explanatory mechanistic variables included markers of oxidative stress (ascorbate/dehydroascorbate, nitric oxide-production cofactor tetrahydrobiopterin and its oxidation product dihydrobiopterin) and inflammation markers (C-reactive protein and leukocyte differential counts). Results: Nitroglycerin-induced vasodilation was reduced by 12% [95% confidence interval: -22%; -1.0%] following PM exposure, whereas hyperemia-induced vasodilation was reduced by 5% [95% confidence interval: -11.6%; 1.6%]. Moreover, HRV measurements showed that the high and low frequency domains were significantly decreased and increased, respectively. Redox and inflammatory status did not change significantly based on the above measures. Conclusions: This study indicates that exposure to real-life levels of PM from urban street air impairs the vasomotor function and HRV in overweight middle-aged and elderly adults, although this could not be explained by changes in inflammation, oxidative stress or nitric oxide-cofactors. [ABSTRACT FROM AUTHOR]

We develop confidence intervals (CIs) for quantiles when applying variance-reduction techniques (VRTs) and sectioning. Similar to batching, sectioning partitions the independent and identically distributed (i.i.d.) outputs into nonoverlapping batches and computes a quantile estimator from each batch. But rather than centering the CI at the average of the quantile estimators across the batches, as in batching, sectioning centers the CI at the overall quantile estimator based on all the outputs. A similar modification is made to the sample variance, which is used to determine the width of the CI. We establish the asymptotic validity of the sectioning CI for importance sampling and control variates, and the proofs rely on first showing that the corresponding quantile estimators satisfy a Bahadur representation, which we have done in prior work. Here, we present some numerical results. [ABSTRACT FROM AUTHOR]

Background: Despite their different appearance on imaging, hemorrhagic and ischemic vascular lesions frequently co-occur in the brain and are hypothesized to progress concurrently. Although silent hemorrhagic and ischemic vascular brain lesions are highly prevalent in the general population, the concomitant progression of these lesions has only been studied to a limited extent in this population. We therefore aimed to investigate whether pre-existing and incident cerebral microbleeds (CMBs) are related to the progression of ischemic lesions in the general population. Methods: In the prospective population-based Rotterdam Scan Study, 803 individuals aged ≥60 years underwent magnetic resonance imaging at baseline and after an average interval of 3.4 years. The presence of microbleeds and lacunes was visually rated by trained research physicians, and white matter lesions (WMLs) were automatically segmented at both time points. Logistic regression was used to investigate the association of microbleeds with incident lacunes, and linear regression was used to investigate the relation between microbleeds and progression of WML volume. All analyses were adjusted for age, sex and the time interval between baseline and follow-up scanning. The analyses were repeated after additional adjustments for cardiovascular risk factors: blood pressures; total and high-density lipoprotein cholesterol; smoking; diabetes mellitus; lipid lowering, antihypertensive and antiplatelet medications, and apolipoprotein E ε4. The analyses involving WMLs were also adjusted for intracranial volume. Results: We found that pre-existing microbleeds in any location of the brain were related to a higher incidence of lacunes (odds ratio [OR] adjusted for age, sex and scan interval: 4.67; 95% confidence interval [CI]: 1.84-11.85). Pre-existing microbleeds were not related to progression of WML volume (mean difference in WML volume increase: -0.03; 95% CI: -0.15 to 0.09). Additional adjustments for cardiovascular risk factors did not change the results considerably. Incident microbleeds in any location of the brain were associated with a higher incidence of lacunes (OR: 9.18; 95% CI: 3.61-23.35), whereas only incident microbleeds located in cortico-subcortical regions were related to progression of WML volume (mean difference in WML volume increase: 0.41; 95% CI: 0.21-0.62). Again, adjustments for cardiovascular risk factors did not change the results significantly. Conclusions: Our findings suggest that in the general population, CMBs serve as a predictor of ischemic brain lesions and may represent an imaging marker of active vasculopathy. These results support the hypothesis of a common underlying pathway in the development of ischemic and hemorrhagic brain lesions. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Data on attrition due to mortality or loss to follow-up (LTFU) from antiretroviral therapy (ART) eligibility to ART initiation of HIVinfected children are scarce. The aim of this study is to describe attrition before ART initiation of 247 children who were eligible for ART in a cohort study in India. Multivariable analysis was performed using competing risk regression. The cumulative incidence of attrition was 12.6% (95% confidence interval, 8.7- 17.3) after five years of follow-up, and the attrition rate was higher during the first months after ART eligibility. Older children (>9 years) had a lower mortality risk before ART initiation than those aged <2 years. Female children had a lower risk of LTFU before ART initiation than males. Children who belonged to scheduled tribes had a higher risk of delayed ART initiation and LTFU. Orphan children had a higher risk of delayed ART initiation and mortality. Children who were >3 months in care before ART eligibility were less likely to be LTFU. The 12-month risk of AIDS, which was calculated using the absolute CD4 cell count and age, was strongly associated with mortality. A substantial proportion of ART-eligible children died or were LTFU before the initiation of ART. These findings can be used in HIV programmes to design actions aimed at reducing the attrition of ART-eligible children in India. [ABSTRACT FROM AUTHOR]

Background: Severe neonatal encephalopathy (NE) of hypoxic-ischaemic origin may cause death or life-long disability. Acute encephalopathy may also affect cerebrovascular control. Pourcelot's cerebrovascular resistance index (RI) ≤0.55 was predictive of poor outcome in normothermic NE infants. Recent studies have questioned its predictive power during therapeutic hypothermia (HT). Objective: To assess the predictive power of RI during HT and after rewarming. Methods: 45 infants with NE treated with HT for 72 h had their RI calculated during early (median 11 h) and late (median 62 h) cooling and after rewarming (median 89 h). Poor outcome was defined as death or abnormalities on day 10 magnetic resonance imaging shown to predict severe neuromotor disability. Results: RI ≤0.55 during cooling did not differentiate between good and poor outcome (late cooling, p = 0.08), but was powerful after rewarming (p = 0.004). RI ≤0.55 predicted true poor outcome in 43% (95% confidence interval (CI): 12, 80) during late cooling and in 100% (95% CI: 31, 100) after rewarming. RI >0.55 predicted good outcome in 86% (95% CI: 69, 95) during late cooling and in 89% (95% CI: 74, 96) after rewarming. Conclusions: Low RI is not predictive of poor outcome during HT in NE infants, but regains the predictive power seen in normothermic infants after rewarming. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Matched-pair design is often used in clinical trials to increase the efficiency of establishing equivalence between two treatments with binary outcomes. In this article, we consider such a design based on rate ratio in the presence of incomplete data. The rate ratio is one of the most frequently used indices in comparing efficiency of two treatments in clinical trials. In this article, we propose 10 confidence-interval estimators for the rate ratio in incomplete matched-pair designs. A hybrid method that recovers variance estimates required for the rate ratio from the confidence limits for single proportions is proposed. It is noteworthy that confidence intervals based on this hybrid method have closed-form solution. The performance of the proposed confidence intervals is evaluated with respect to their exact coverage probability, expected confidence interval width, and distal and mesial noncoverage probability. The results show that the hybrid Agresti–Coull confidence interval based on Fieller’s theorem performs satisfactorily for small to moderate sample sizes. Two real examples from clinical trials are used to illustrate the proposed confidence intervals. [ABSTRACT FROM AUTHOR]

Simulations not only facilitate new and unprecedented insights in highly sophisticated science areas, but also support product design in engineering in terms of improved functionality, cost and time issues. However, as a matter of fact, simulations examine limited excerpts of real systems with accompanying simplifications, abstractions and idealizations. Hence, there is a distinct need to be aware of upcoming risks in simulation outcomes caused by uncertainties. These influence every step of forward-thinking simulation design which is not only restrained by modeling practice but begins with reality perception itself.The intention of the paper is to embed an awareness of uncertainty in the context of simulation by linking major classes of uncertainty with uncertainties within simulations in engineering design. Besides the decisive inclusion of reality as the starting point, mathematic approaches are also used to understand how those uncertainty classes evolve through exponential knowledge creation of systems. The transfer to statistical tolerance analysis shall finally put emphasis on the practical classification of uncertainty, starting from data preparation via concept design and mathematical implementation to result depiction. In the end, the reader’s conception of possible uncertainties in special simulation cases shall be sharpened which, vice versa, shall lead to even better and well-thought-out simulation outcomes. [ABSTRACT FROM PUBLISHER]

Background This study compared the risk of fatal cerebrovascular accidents (CVAs) in patients with early-stage glottic laryngeal cancer receiving surgery or external beam radiation therapy (EBRT). Methods Using a competing risks survival analysis, we compared the risk of death because of CVA among patients with early-stage glottic laryngeal cancer receiving surgery or EBRT in the Surveillance, Epidemiology, and End Results (SEER) database. Results The cumulative incidence of fatal CVA at 15 years was higher in patients receiving EBRT (2.8%; 95% confidence interval [CI], 2.3% to 3.4%) compared to surgery (1.5%; 95% CI, 0.8% to 2.3%; p = .024). In multivariable competing risks regression models, EBRT remained associated with an increased risk of fatal CVA compared to surgery (adjusted hazard ratio [HR], 1.75; 95% CI, 1.04-2.96; p = .037). Conclusion Treatment for early-stage glottic laryngeal cancer with EBRT was associated with a small increase in the risk of late fatal CVA events relative to surgery. © 2013 Wiley Periodicals, Inc. Head Neck 36: 611-616, 2014 [ABSTRACT FROM AUTHOR]

Background The purpose of this study was to comprehensively and quantitatively summarize the prognostic value of microvessel density (MVD) and lymphatic vessel density (LVD) for the survival of patients with head and neck squamous cell carcinoma (HNSCC). Methods Relevant literatures were identified using Medline and EMBASE. A meta-analysis was performed to clarify the prognostic role of MVD and LVD. Results A total of 18 articles (13 for MVD and 5 for LVD; n = 1279 and n = 408) were pooled for the global meta-analysis. The mortality was 1.23-fold higher for patients whose MVD counts were above the cutoff (risk ratio [RR], 1.23; 95% confidence interval [CI], 0.99-1.52), compared with those below it, and this result was on a borderline ( p = .06). The mortality of patients with high LVD counts was 2.07-fold higher (RR, 2.07; 95% CI, 1.16-3.71; p = .01). Conclusion High counts of LVD, not MVD, are associated with worse 5-year overall survival (OS) in patients with HNSCC. © 2013 Wiley Periodicals, Inc. Head Neck 36: 596-602, 2014 [ABSTRACT FROM AUTHOR]

We propose robust methods for inference about the effect of a treatment variable on a scalar outcome in the presence of very many regressors in a model with possibly non-Gaussian and heteroscedastic disturbances. We allow for the number of regressors to be larger than the sample size. To make informative inference feasible, we require the model to be approximately sparse; that is, we require that the effect of confounding factors can be controlled for up to a small approximation error by including a relatively small number of variables whose identities are unknown. The latter condition makes it possible to estimate the treatment effect by selecting approximately the right set of regressors. We develop a novel estimation and uniformly valid inference method for the treatment effect in this setting, called the “post-double-selection” method. The main attractive feature of our method is that it allows for imperfect selection of the controls and provides confidence intervals that are valid uniformly across a large class of models. In contrast, standard post-model selection estimators fail to provide uniform inference even in simple cases with a small, fixed number of controls. Thus, our method resolves the problem of uniform inference after model selection for a large, interesting class of models. We also present a generalization of our method to a fully heterogeneous model with a binary treatment variable. We illustrate the use of the developed methods with numerical simulations and an application that considers the effect of abortion on crime rates. [ABSTRACT FROM PUBLISHER]

Abstract: Background: There are little published data on outcomes of blood conservation (BC) patients after noncardiac surgery. The objective of this study was to compare the surgical outcomes of patients enrolled in our BC program with that of the general population of surgical patients. Methods: BC patients at our institution undergoing various surgical procedures were identified from the 2007–2009 National Surgical Quality Improvement Program database and compared with a cohort of conventional care (CC) patients matched by age, gender, and surgical procedure. Univariate and multiple logistic regression analyses were performed to evaluate 30-d postoperative outcomes. Results: One hundred twenty BC patients were compared with 238 CC patients. The two groups were similar for all preoperative variables except smoking, which was lower in the BC group. On univariate analysis, BC patients had similar mean operating time (148 versus 155 min; P = 0.5), length of stay (5.9 versus 5.5 d; P = 0.7), and rate of return to the operating room (7.5% versus 5.5%; P = 0.4) compared with CC patients. BC and CC patients had similar 30-d morbidity (18% versus 14%; P = 0.3) and mortality rates (1.6% versus 1.3%; P = 1.0), respectively. On multivariable analysis, enrollment in the BC program had no impact on postoperative 30-d morbidity (odds ratio, 1.78; 95% confidence interval, 0.71–4.47) or 30-d mortality (unadjusted odds ratio, 1.33; 95% confidence interval, 0.22–8.05). Conclusions: Short-term postoperative outcomes in BC patients are similar to the general population, and these patients should not be denied surgical treatment based on their unwillingness to receive blood products. [Copyright &y& Elsevier]

Purpose: To determine whether a Fas-associated via death domain (FADD) promoter single-nucleotide polymorphism (SNP) is associated with susceptibility to papillary thyroid cancer (PTC) and clinicopathological features of PTC. Methods: To identify a possible association with PTC, 94 patients with PTC and 346 healthy controls were recruited. One promoter SNP (rs10898853, -16C/T) was analyzed by direct sequencing. Multiple logistic regression models (co-dominant, dominant, recessive, and log-additive models) were applied, and odds ratios (ORs), 95% confidence intervals (CIs), and p values were calculated. Results: The genotype of the promoter SNP (rs10898853) of FADD was found to be significantly associated with PTC in the co-dominant model 2 (T/T vs. C/C; p = 0.002, OR = 2.80, 95% CI = 1.39-5.65), the recessive model (p = 0.003, OR = 2.21, 95% CI = 1.31-3.71), and the log-additive model (p = 0.002, OR = 1.71, 95% CI = 1.20-2.44). Allele frequency analysis showed that the C allele of rs10898853 was significantly associated with an increased risk of PTC (p = 0.002, OR = 1.67, 95% CI = 1.21-2.32). Conclusions: Our results suggest that the FADD promoter polymorphism is associated with susceptibility to PTC. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]