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Analysis of data from group‐randomized trials with repeat observations on the same groups
Author(s) -
Murray David M.,
Hannan Peter J.,
Wolfinger Russell D.,
Baker William L.,
Dwyer James H.
Publication year - 1998
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/(sici)1097-0258(19980730)17:14<1581::aid-sim864>3.0.co;2-n
Subject(s) - statistics , analysis of variance , mathematics , one way analysis of variance , mixed design analysis of variance , confidence interval , variance (accounting) , sampling (signal processing) , repeated measures design , random effects model , type i and type ii errors , sample size determination , econometrics , computer science , medicine , meta analysis , accounting , filter (signal processing) , business , computer vision
This study used Monte Carlo simulations to evaluate the performance of alternative models for the analysis of group‐randomized trials having more than two time intervals for data collection. The major distinction among the models tested was the sampling variance of the intervention effect. In the mixed‐model ANOVA, the sampling variance of the intervention effect is based on the variance among group×time‐interval means. In the random coefficients model, the sampling variance of the intervention effect is based on the variance among the group‐specific slopes. These models are equivalent when the design includes only two time intervals, but not when there are more than two time intervals. The results indicate that the mixed‐model ANOVA yields unbiased estimates of sampling variation and nominal type I error rates when the group‐specific time trends are homogenous. However, when the group‐specific time trends are heterogeneous, the mixed‐model ANOVA yields downwardly biased estimates of sampling variance and inflated type I error rates. In contrast, the random coefficients model yields unbiased estimates of sampling variance and the nominal type I error rate regardless of the pattern among the groups. We discuss implications for the analysis of group‐randomized trials with more than two time intervals. © 1998 John Wiley & Sons, Ltd.