Statistically Corrected

Met Prof Baharuddin today for sample size calculation. He's the reknowned statistician in the whole of FSKB, UKM. He actually pursued statistics because he loves it. Hard to believe anyone could ever love the complexity of statistics but I guess someone has to right? If not who will teach us ignorant students :).
Anyway.
He told me the formula that I used for the proposal presentation was absolutely wrong because that particular formula is actually for those doing a prevalence study. So malu! coz pandai-pandai saja, hehe.Blushingly, I asked him what is the right formula for my study.
He asked me what is the study and I just handed him a copy of my proposal presentation. First, he corrected my title, to quote 'it should be among older adults not in older adults'. 'Aye aye sir' I said to myself, and thought, 'hrmm, funny how the deputy dean @ my supervisor had let it pass and I am corrected by the statistician whom I am meeting for the first and probably last time'. He arrived to the objective of my study on measuring benefits, so after scrutinizing the very small font of my statistics notes, taught me to use which values to put in in the most suitable formula.
He advised me to do a pilot study on 20 subjects that fulfill the inclusive and exclusive criteria in order to get the values. Being a smart-alec, I was like, '20 subjects?? Okay... can I use the results from the pilot study's subjects as the results for the real study's subjects?'
And he said I can't. I then whined on where am I going to find so many subjects and he said to me that if you want to simply guess the number of subjects, don't come and find him to innocently ask him to teach and then not applying what is taught. I came to my senses and agreed, because it's like an insult to him right, if I do so.
After that he relented and said I can use 10 subjects for the pilot study. I asked him if he wants to be my subject and he agreed! Yay. So i guess it was kind of a win-win situation where he got his msg across to me (on understanding what he said and applying it) and I get a subject in return.
Hope he's a cooperative subject, that is, if he fulfills the subject's criterion first, of course :)