I am designing a clinical trial to test the efficacy of a new therapeutic modality of bone fusion. I plan to run a double blind superiority study to prove clinical efficacy. In my preparation for estimating the study size I have calculated that the efficacy of this device will be around 10% better than a placebo. Furthermore, there will be some variability in the data due to drug effects (which I can identify, but not control for). Previous similar studies have used between 220 - 350 patients.
My question is this: If I assume that a placebo group (no treatment) demonstrates improvement in bone growth among 40% of the patients, will I need a larger sample size to power the study, than if I assume 65% of the placebo group will demonstrate improvement in bone growth? Please provide an answer with a simple example for this statistically-challenged researcher. Thanks Jay . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
