Hi Thomas, Thanks for the reply.
1. In the first pick, I draw 'A' genes from N, without replacement. 2. Similarly, in the second pick, I draw 'B' genes from N, without replacement (and 'C' genes from 'N' etc.) 3. Order does not matter - so the two cases you cited are equivalent. I would like to find out the probability that 'n' of the genes are common to all three 'picks'. many thanks! ________________________________ From: Thomas Stewart <tgstew...@gmail.com> Cc: r-help@r-project.org Sent: Mon, October 4, 2010 10:46:37 AM Subject: Re: [R] Fisher exact test? To find the probability directly, you'll need to clearly state how you are sampling. Are you sampling with replacement? (Draw then put back.) Or are you sampling without replacement? (Draw. Draw from the remaining. Draw from the remaining.) Also, of the N genes, do you know how many are of the particular set? How many genes do you draw each try? Does order matter to you? In other words is (A=5, B=0, C=23) equivalent to (A=0,B=5,C=23)? -tgs Hi All, > >My apologies if this is a totally newbie question. > >I want to calculate the probability that a particular set of genes is picked >repeatedly for 3 samplings. For example, if from a total of 'N' genes, I pick >'A' number of genes in the first pick, 'B' number of genes in the second pick, >and 'C' number of genes in the third pick, I would want to calculate p(n) where >n = (A intersection B intersection C). > >Would fisher exact test be the correct method to evaluate the probability? And >if so how can I frame the 3x3 (?) contingency table? I can find numerous >examples of 2x2 tables, but none for 3x3. Any guidance would be appreciated. > >many thanks. > > > > [[alternative HTML version deleted]] > >______________________________________________ >R-help@r-project.org mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
