This class was difficult in the sense that I didn't really understand much and failed most of the problem sets but then I got an A for the semester! I think it's graded more on effort. If you are not math-inclined at all and need a math/stat QS, this is a perfect class. Also learned some interesting things I hadn't thought about mathematically before (voting, sharing food, etc.)
Very great class! I took it my freshman year and was not disappointed. Not only is it fun (applications of math are cool and intuitive), but it is also unlike like most duke math classes very easy!