Comparing different ways of calculating sample size for two independent means: A worked example.

ABSTRACT: We discuss different methods of sample size calculation for two independent means, aiming to provide insight into the calculation of sample size at the design stage of a parallel two-arm randomised controlled trial (RCT). We compare different methods for sample size calculation, using published results from a previous RCT. We use variances and correlation coefficients to compare sample sizes using different methods, including 1. The choice of the primary outcome measure: post-intervention score vs. change from baseline score. 2. The choice of statistical methods: t-test without using correlation coefficients vs. analysis of covariance (ANCOVA). We show that the required sample size will depend on whether the outcome measure is the post-intervention score, or the change from baseline

SUBMITTER: Clifton L 

PROVIDER: S-EPMC6297128 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature