Donald Hedeker, Robert D. Gibbons, Christine Waternaux
Formulas for estimating sample sizes are presented to provide specified levels
of power for tests of significance from a longitudinal design allowing for
subject attrition. These formulas are derived for a comparison of two groups in
terms of single degree-of-freedom contrasts of population means across the study
timepoints. Contrasts of this type can often capture the main and interaction
effects... hiện toàn bộ
For the comparison of more than two independent samples the Kruskal-Wallis H
test is a preferred procedure in many situations. However, the exact null and
alternative hypotheses, as well as the assumptions of this test, do not seem to
be very clear among behavioral scientists. This article attempts to bring some
order to the inconsistent, sometimes controversial treatments of the
Kruskal-Wallis te... hiện toàn bộ
The tetrachoric correlation describes the linear relation between two continuous
variables that have each been measured on a dichotomous scale. The treatment of
the point estimate, standard error, interval estimate, and sample size
requirement for the tetrachoric correlation is cursory and incomplete in modern
psychometric and behavioral statistics texts. A new and simple method of
accurately appr... hiện toàn bộ
Imputation methods are popular for the handling of missing data in psychology.
The methods generally consist of predicting missing data based on observed data,
yielding a complete data set that is amiable to standard statistical analyses.
In the context of Bayesian factor analysis, this article compares imputation
under an unrestricted multivariate normal model (Multiple Imputation [MI]) to
imputa... hiện toàn bộ