Now before I calculate the correlation coefficient, let's just make sure we understand some of these other statistics that they've given us. So we assume that these are samples of the x and the corresponding y from a broader population. And so we have the sample mean for x and the sample standard deviation for x. The sample mean for x is quite straightforward to calculate. It would just be one plus two plus two plus three over four, and this is eight over four, which is indeed equal to two. The sample standard deviation for x, we've also seen this before. This should be a little bit of review.