Research rambling, possibly boring (I can't tell).

My dissertation is about child physical abuse. (I'm not going to get into the details about which aspects at the moment. Maybe later.) Now, you can't come right out and ask parents, "so, do you abuse your kids?" - not if you want accurate answers. You can't very easily ask minor children what their parents do to them - not as research, anyway. You can limit your subject population to people who have been investigated or convicted of child abuse - lots of people do that - but you always wind up wondering whether there's a difference between the ones Child Protective Services have identified and the ones who haven't been caught. (The answer is almost certainly "yes.")
( so here's what we do. )