Because the formula used here is based on approximating the t statistic with a z statistic, it will slightly underestimate the sample size when N is less than about 30.

Software utilities by Michael Kohn (makohn@mkanders.com) and Mike Jarrett (mike.jarrett@quesgen.com)

Disclaimer: Software is provided on an as-is basis and no warranty is made of any kind. Calculations are believed accurate but should be verified by the user