Part II - BEBAC • Consultancy Services for Bioequivalence

6/6 | Statistical Design and Analysis IIIQuote from RV Lenthinformalife sciencesThere is simple intuition behindresults like these: If my car madeit to the top of the hill, then it ispowerful enough to climb that hill;if it didn’t, then it obviously isn’tpowerful enough. Retrospectivepower is an obvious answer to arather uninteresting question. Amore meaningful question is toask whether the car is powerfulenough to climb a particular hillnever climbed before; or whethera different car can climb that newhill. Such questions areprospective, not retrospective.Bioequivalence and Bioavailability, Pre-Conference Workshop | Ljubljana, 17 May 2010The fact that retrospective poweradds no new information isharmless in its own right.However, in typical practice, it isused to exaggerate the validity ofa significant result (“not only is itsignificant, but the test is reallypowerful!”), or to make excusesfor a nonsignificant one (“well, Pis .38, but that’s only because thetest isn’t very powerful”). Thelatter case is like blaming themessenger.RV LenthTwo Sample-Size Practices that I don't recommendhttp://www.math.uiowa.edu/~rlenth/Power/2badHabits.pdf69 • 68