00:01
So in number one, we want the hypotheses.
00:04
And we would be assuming that the mean is 20 and that alternately the mean is not 20.
00:11
She didn't know whether it was higher or lower.
00:14
And so question two, it's going to be a two -tail test because she doesn't have a direction in which she thinks that this mean might be.
00:23
And we want to know what type of a statistic we're going to, our distribution, we're going to work with a z distribution.
00:30
With a z curve.
00:32
And that is because we know the population standard deviation is two.
00:38
So we'll use a z distribution.
00:42
And on number four, we want to know what the critical values are.
00:45
And we're to use an alpha level of 0 .01.
00:48
And so for a two -tail test, we have to split our alpha into two tails.
00:56
So half of it has to go in each tail.
00:59
And so our critical values are z values that have 0 .005 in the upper tail and 0 .005 in the lower tail.
01:08
And those values are critical values of 2 .576 and negative 2 .576.
01:19
And if we have values that are greater than this value, that will cause us to reject the null.
01:26
And if we have those values less than this value, that will cause us to reject the null.
01:31
Reject the null.
01:34
Now on question five, might as well come back up here, we want to find what the test statistic is, that z value.
01:42
So we take the x bar that she got minus the mean she's assuming, and we take the population standard deviation divided by the sample size, and this comes out to be a z value of negative three.
01:58
Now number six asks us to find the p value, and the p value, and the p value is the likelihood of getting a z value that is less than or equal to negative 3 or greater than or equal to positive 3 because it's a two -tale test...