A SAS macro for sample size re-estimation
Zellner, D.; Zellner, G.E.; Keller, F.
Computer Methods and Programs in Biomedicine 65(3): 183-190
2001
ISSN/ISBN: 0169-2607 PMID: 11339980 DOI: 10.1016/s0169-2607(00)00119-xDocument Number: 513774
The assessment of sample size in clinical trials comparing means requires a variance estimate of the main efficacy variable. If no reliable information about the variance of the key response is available at the beginning of a clinical trial, the use of data from the first 'few' patients entered in the trial ('internal pilot') may be appropriate to estimate the variance and thus to recalculate the required sample size. A SAS macro that implements the EM algorithm for carrying out and simulating such interim power evaluations without unblinding the treatment status is presented.