Here's an image I came across online:
If your friend were to post this on Facebook, probably the first thing you'd need to do would be to have him clarify what claim he's making, since the image doesn't state any conclusions from its data. What questions would you ask to have him clarify his position and to challenge him? Once his position is clear, how would you refute it?
Give us your thougths in the comments below, and then we'll hear from Jim on Thursday with his answer.