Because we want to square the total sum of squares between each data point and their respective means. So let's do that. So it's 3 minus, the mean here is 2 squared, plus 2 minus 2 squared, plus 1 minus 2 squared. Plus, I'm going to do this for all of the groups, but for each group, the distance between each data point and its mean. So plus 5 minus 4 squared. Plus 4 minus 4 squared. And then finally we have the third group.