 Hello, this is a video on one sample hypothesis testing, finding the critical value. In my example, we are performing a two-tailed Z test. So we're dealing with the standard normal distribution that has a mean of 0, standard deviation of 1. If alpha equals 0.02, find the positive critical value. So you may be wondering why in the world they put the word positive here. The reason why is because anytime you have a two-tailed test, there are two critical values. Because of symmetry related to the bell curve and the fact that the mean of the standard normal distribution is 0, these two critical values are opposites of each other. Two critical values are opposites of each other. Since this is a two-tailed test, I'm going to go ahead and mark off my two tails. And I'll have some negative critical value and some positive critical value. The positive is the one that I want in this case. Now if you recall from a previous video to find a critical value, you have to use alpha. Alpha is the area of the tails. My alpha is 0.02. Since I have two tails, I have to divide this 0.02 by 2 to get 0.01. So 0.01 in the left tail, 0.01 in the right tail. Now looking at my positive critical value I would like to find, I need to know area to the left. Well, area to the left is 1 minus the area to the right. So 1 minus 0.01, which is going to give us 0.99 in this case. So whenever I go to find my positive critical value, I know that my mean is 0. My standard deviation is 1. And my area to the left is equal to 0.99. In Google Sheets, you'll go to the Compute tab. We're still dealing with the normal area here, or normal region. The mean is still 0. Standard deviation is 1. And the left tail area is actually 0.99. That is the area to the left of the data value, or critical value I'm trying to find. I get about 2.33, 2.33. So my positive critical value is 2.33. Well, remember what I said at the beginning? I said two tail tests have two critical values. They are opposites of each other. So if my positive critical value is 2.33, my negative critical value should be negative 2.33. Let's check this. The area to the left of my negative critical value is 0.01. In Google Sheets, let's change the area to the left, 2.01. And look what happens. Same answer, except now it's just the opposite with the negative sign. So that's just to show you that the two critical values of a two tailed test are actually always going to be opposites of each other. So that's all I have for you for now. Thanks for watching.