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...

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...

Different methods of determining formation rates of 3 nm particles are compared, basing on analysis of simulated data, but the results are valid for analyses of experimental particle size distribution data as well, at least within the accuracy of the applied model. The study shows that the method of determining formation rates indirectly from measured number concentration data of 3–6 nm particl...

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 ...

In the main approaches used to elicit consumer preference for food attributes, only limited attribute information are present. Though useful for ranking and revealing consumer preferences, these methods are not appropriate when results may be dependent upon the information set presented in the surveys. Studies have found out that additional quality information in surveys significantly affected ...