And over here we would put 2.5%. And over here we would have 2.5%. And we would have 95% in the middle. So we need to find this critical z-score, critical z value, and if our z value is greater than the positive version of this critical z value, then that's less probable than the odds of getting something so extreme is less than 5%. And we can, assuming the null hypothesis is correct, so then we can reject the null hypothesis. So let's see what this critical z value is. So essentially we want a z value where the entire percentage below it is going to be 97.5%, because then you're going to have 2.5% over here.