SAMPLE-SIZE REQUIREMENTS FOR STRATIFIED PROSPECTIVE STUDIES WITH NULLHYPOTHESIS OF NON-UNITY RELATIVE RISK USING THE SCORE TEST

The standard test of the null hypothesis of unity of the relative risk seeks to determine if two treatments differ. It does not apply when t he requirement is either to establish the equivalence of two treatment s or to determine whether the relative risk is less than a specified v alue other than one. This paper presents the asymptotic power function of the score test for the null hypothesis of a specified value of a c ommon relative risk for stratified prospective studies and proposes an approximate formula for the sample size required for a specific power of the test. One can obtain a sample size formula for stratified stud ies with the standard null hypothesis of unity relative risk as a spec ial case of this formula.