I'm studying for the PCAT and have come across a few variance questions. I feel like they are just oversimplying the heck out variance. I'll post one of the latest questions ... [PLAIN]http://img825.imageshack.us/img825/1875/32561537.jpg [Broken] The explanation they give is because Class A has a larger range of scores (19 vs. 17) it "suggests" that the variation is greater. I really don't think they want me to find the expected value and then subtract each score from that and then square it and w/e else to find the exact variance. So is just looking at a range of scores a decent rule of thumb to compare variation between different data groups? Or would I need some pre-req like they atleast need to have similar mean values?