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? Well, we need a result, so we need some critical z-value here, some critical z-score, or some critical, I should actually say some critical value here, because this isn't a normalized standard. This isn't a normalized normal distribution. But so there's some critical value here.