bettywong

yes..there are secondary hypothesis to be tested in the cohort..the significance level will be corrected according to the number of tests So...to summarize, if I understood properly from your posts, this difference (allele freq.) is somehow expected given sampling issue across whole Japan (consisting of several islands). To combine or not, depends on what I want to answer in my study given different samples I have. For example, 2 genes were investigated in Japanese and Taiwanese, the main hypothesis is to see any difference existing in cases and controls in Asian population. One gene showed quite similar allele/genotype freq. in the controls of the 2 populations, I think I could combine them; for the other gene, which showed differed distribution in the 2 populations, may be due to positive selection or sampling bias, I should do seperate analysis directly. Would you agree?

The hypothesis is to test any difference between cases and controls (i.e., genotype frequency difference) in Asian population, including subjects from Japan and Taiwan (both having their own cases and controls). So, I think I better analyze them seperately given the problem I have? May I ask, under what kind of hypothesis, that you could combine them? Couldn't think of an example by myself, thanks indeed.

Thank you, I agree You mean if the two results highly matched?

Hello everybody, I'm new to this forum. I was searching online where I could ask a genetic question, as I got stuck in my work...then I found here....any opinions are much appreciated... Okay, jump into the problem...I'm doing a genetic association study, and considering to combine 2 East Asian population (i.e., Japanese and Taiwanese) as one to somehow increase the sample size, thus improve the power of the study. But I found out the gene we are looking at showed different allele frequency distributions in Japanese and Taiwanese, e.g., A-allele frequency is 0.48 and a-allele freq. is 0.52 in Japanese; but A-allele freq. 0.56, a-allele freq 0.44 in Taiwanese for the same gene. Can I still combine them as one Asian group for analysis, or I should consider population substructure seriously in this case, thus analyze them seperately? Thank you for your help..