Ok I need someone with more brain power (or some knowledge of statistics) I have two sets of related data. Set A was carried out in 2008 and had 800 respondents. Set B was carried out in 2010 and had 40 respondents. The questions used in both sets are the same. Obviously Set B has a smaller response rate. Is there a mathematical way of comparing the validity of Set B results to Set A ? Hope that makes sense, and I hope I given enough information.