Send to

Choose Destination
See comment in PubMed Commons below
Comput Methods Programs Biomed. 2001 Feb;64(2):121-124.

Sample size and power calculations in repeated measurement analysis.

Author information

  • 1University of Texas Health Science Center at Houston, 6431 Fannin St., MSB 1.112, 77030, Houston, TX, USA.


Controlled clinical trials in neuropsychopharmacology, as in numerous other clinical research domains, tend to employ a conventional parallel-groups design with repeated measurements. The hypothesis of primary interest in the relatively short-term, double-blind trials, concerns the difference between patterns or magnitudes of change from baseline. A simple two-stage approach to the analysis of such data involves calculation of an index or coefficient of change in stage 1 and testing the significance of difference between group means on the derived measure of change in stage 2. This article has the aim of introducing formulas and a computer program for sample size and/or power calculations for such two-stage analyses involving each of three definitions of change, with or without baseline scores entered as a covariate, in the presence of homogeneous or heterogeneous (autoregressive) patterns of correlation among the repeated measurements. Empirical adjustments of sample size for the projected dropout rates are also provided in the computer program.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Support Center