The residuals of a least squares regression model are defined as the observations minus the modeled values. For least squares regression to produce valid CIs and P values, the residuals must be independent, be normally distributed, and have a constant variance. If these assumptions are not satisfied, estimates can be biased and power can be reduced. However, there are ways to assess these assum...

We consider the problem of sample size determination for three-level mixed-effects linear regression models for the analysis of clustered longitudinal data. Three-level designs are used in many areas, but in particular, multicenter randomized longitudinal clinical trials in medical or health-related research. In this case, level 1 represents measurement occasion, level 2 represents subject, and...

In the problem of high-dimensional convexity testing, there is an unknown set S ⊆ R which is promised to be either convex or ε-far from every convex body with respect to the standard multivariate normal distribution N (0, 1). The job of a testing algorithm is then to distinguish between these two cases while making as few inspections of the set S as possible. In this work we consider sample-bas...

The problem of hypothesis testing about proportions in two Ž nite populationsis addressed.The usual test based on the normal approximation (Z test) and a test based on estimatedp values (E test) are considered. The exact properties of the tests are evaluated numerically. Numerical studies indicate that the E test is very satisfactory even for small samples and can be recommended for practical u...

This paper develops a modified version of the Sargan (1958, Econometrica 26(3): 393-415) test statistic of overidentifying restrictions, and shows that it is numerically equivalent to the test statistic of Hahn and Hausman (2002, Econometrica 70(1): 163-189) up to a sign. The modified Sargan test is constructed such that its asymptotic distribution under the null hypothesis of correct specifica...

BACKGROUND The evaluation of more than one intervention in the same randomised controlled trial can be achieved using a parallel group design. However this requires increased sample size and can be inefficient, especially if there is also interest in considering combinations of the interventions. An alternative may be a factorial trial, where for two interventions participants are allocated to ...

The aim of this investigation was to look at user groups of institutional repositories. Past research on repository users has focused on authors and depositors at the expense of other users, and little is known about what types of user groups are associated with institutional repositories. This investigation used the research techniques of link analysis and content analysis ...

Cross-sectional analytical and case-control studies are commonly reported study designs in clinical and public health research. Clinicians and researchers often get confused between them. Both are analytical observational studies, compare two study groups, and collect the data at one time from the study participants. However, the point of initiation of the study and interpretation of the result...

We study the problem of collaborative clustering. This problem is concerned with a set of items grouped into clusters that we wish to recover from ratings provided by users. The latter are also clustered, and each user rates a random but typical small number of items. The observed ratings are random variables whose distributions depend on the item and user clusters only. Unlike for collaborativ...

A common assumption in meta-analysis is that effect sizes are independent. When correlated effect sizes are analyzed using traditional univariate techniques, this assumption is violated. This research assesses the impact of dependence arising from treatment-control studies with multiple endpoints on homogeneity measures Q and I(2) in scenarios using the unbiased standardized-mean-difference eff...