How many repeated measurements are useful?

✍ Scribed by John E. Overall

• Book ID: 102654723
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 798 KB
• Volume: 52
• Category: Article
• ISSN: 0021-9762
• DOI: 10.1002/(sici)1097-4679(199605)52:3<243::aid-jclp1>3.0.co;2-t

✦ Synopsis

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 maid 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.