So the sum of squares within. Let me make it clear. That stands for within. So we want to see how much of the variation is due to how far each of these data points are from their central tendency, from their respective means. So this is going to be equal to, let's start with these guys. So instead of taking the distance between each data point and the mean of means, I'm going to find the distance between each data point and that group's mean. Because we want to square the total sum of squares between each data point and their respective means.