Rick, thanks for the reply. I'll ask on community, but can I ask a quick question here? I didnt want to use logistic regression since the data is not accounting for much of the variance due to missing information. I just want to know, given the two variables I have, to which of the two groups is a new observation more likely to belong to? So is it valid to compare MDs when the two groups Yes and No have different covariance and mean?