Sample Size Estimation when Comparing More than two Treatment Groups

A large amount of literature has been published on methods for determining sample size and power for clinical trials. Although formulae exist to determine sample size for different designs, in practice the methods are rarely used. Instead, sample size estimates are usually based on simple formulae derived for the comparison of two means or binomial proportions.

This paper describes some useful theory for sample size estimation when comparing more than two treatment groups. Where the theory is not applicable, it is demonstrated that simulation can be used as an alternative approach.