2 ms·

Thanks for answering. Unfortunately in the population studied (white americans) HIV is far more prevalent in men who have sex with men (>70% of all new infecti

Thanks for answering. Unfortunately in the population studied (white americans) HIV is far more prevalent in men who have sex with men (>70% of all new infections) than in heterosexual men and women. If your two populations vary significantly in any factor you need to control for it or make sure you rule out that it is significant - this is science 101. Having read the paper and authors notes, it appears that facial fat differences are unlike to be the signal being detected.

m_mueller 9y ago
You only need to control for it if the total number of infections is a significant percentage (probably somewhere around 1-5% depending on significance level) of each group population - otherwise you'd have to control for anything and everything and statistical field studies would be completely impossible to allow for any conclusions (while as it is it's just really hard).
- danieltillett 9y ago
  This is true, but you should at least make an effort to rule this out. The really hard thing in science is not fooling yourself by overlooking something important.