So if there's less than a 5% probability of this happening, we're going to reject the null hypothesis. And go, less than a 5% probability, given the null hypothesis is true, then we're going to reject the null hypothesis in favor of the alternative. So let's think about this. So we have the null hypothesis. Let me draw a distribution over here. The null hypothesis says that the mean of our differences, so the mean of the differences of the sampling distributions should be equal to 0. Now, in that situation, what is going to be our critical region here?