So it's going to be 6 minus 4 squared plus 6 minus 4 squared plus 6 minus 4 squared. Now let's think about how many degrees of freedom we had in this calculation right over here. How many degrees of freedom? Well, in general, I guess the easiest way to think about it is how much information did we have, assuming that we knew the mean of means. If we know the mean of means, how much here is new information? Well, if you know the mean of the mean and you know two of these sample means, you can always figure out the third. If you know this one and this one, you can figure out that one.