PMID: 9551283Apr 29, 1998Paper

Comparative evaluation of two models for estimating sample sizes for tests on trends across repeated measurements

Controlled Clinical Trials
J E OverallC B Anderson

Abstract

Two equations for calculating sample sizes that are required for power in testing differences in rates of change in repeated measurement designs have been presented by different authors. One equation provides support for the conclusion that increased frequency of measurements across a treatment period of fixed duration enhances power of the tests. The other equation supports the counterintuitive conclusion that increased frequency of measurements actually tends to decrease power in the presence of realistic serial dependencies in the data. Monte Carlo methods confirm that the equation providing support for the latter conclusion is accurate, whereas the alternative equation tends to underestimate sample sizes required for power in testing differences in slopes of regression lines fitted to changes in the repeated measurements across time when symmetry is absent from the covariance structure.

References

Jun 1, 1994·Controlled Clinical Trials·A J KirbyA Muñoz
Apr 1, 1994·Controlled Clinical Trials·J E Overall, S R Doyle

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Citations

Jan 19, 2011·Contemporary Clinical Trials·Song Zhang, Chul Ahn
Dec 4, 2008·Statistics in Medicine·Kaifeng LuGuanghan Liu
Jul 19, 2005·Statistics in Medicine·X M TuR Gallop
May 29, 1999·Journal of Clinical Psychology·J E Overall, R S Atlas
Jun 24, 2000·Journal of Clinical Psychology·J E Overall, C Shivakumar
Mar 26, 1999·Journal of Biopharmaceutical Statistics·J E OverallY Kalburgi

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