There's no difference—are you sure?
Volume 108, Issue 2, Pages 231–232
David R. Meldrum, M.D., H. Irene Su, M.D., M.S.C.E.
In September 2014, we discussed the importance of an a priori sample-size calculation and other considerations in planning and conducting a study to be sure that it is sufficiently powered to detect the smallest clinically relevant effect size. A reader can then interpret an adequately powered, but negative, study to mean that the difference between treatment groups is not larger than that predetermined effect size and can use the information to support therapeutic decisions. Sample-size calculations are now required by many Institutional Review Boards, funding agencies, and medical journals.