Sample Size/Power Calculations

To access this set of programs, in Stata type:

.net from

You will be asked which package you wish to install. Click on screensize. This will install three Stata commands: rocsize, aucsize and srcsize. These commands perform simulation studies to assess the statistical power that a phase 2 study has, i.e., a study to evaluate performance of a single biomarker. See section 8.2 of Pepe (2003) for formulas to calculate sample sizes for a phase 2 study. The formulas are based on asymptotic theory and will not provide exactly the right power in practice. Following the calculations one should run simulation studies and adjust sample sizes until the power is at the desired level. See Pepe (2003, page 220) for discussion. Running these simulations is fun. Try it!

Excerpt from Pepe, MS (2003) The Statistical Evaluation of Medical Tests for Classification and Prediction. Oxford University Press.