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How many repeated measurements are useful?
Author(s) -
Overall John E.
Publication year - 1996
Publication title -
journal of clinical psychology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.124
H-Index - 119
eISSN - 1097-4679
pISSN - 0021-9762
DOI - 10.1002/(sici)1097-4679(199605)52:3<243::aid-jclp1>3.0.co;2-t
Subject(s) - repeated measures design , analysis of variance , covariate , statistics , mixed design analysis of variance , monte carlo method , statistical significance , psychology , variance (accounting) , mathematics , accounting , business
Simulated data for a two‐group repeated measurements design were generated with different numbers of equally‐spaced measurements interposed between baseline and the end of the study. A standard repeated measurements ANOVA for a split‐pilot design was used to test the significance of the between‐groups main effect, the Geisser‐Greenhouse corrected groups x times interaction, and the difference in linear trends across time. The analyses were repeated with and without baseline measurements entered as a covariate in the model. Monte Carlo results confirmed that increasing the number of repeated measurements across a fixed treatment period generally had negative or neutral implications for power of the tests of significance in the presence of serial dependencies that produced heterogeneous correlations among the repeated measurements. © 1996 John Wiley & Sons, Inc.