00:01
For part a, we have that the null hypothesis here will be that the intervention is not effective at treating depression.
00:09
So that would be that the mean difference here is equal to zero.
00:14
The alternate hypothesis will be that the mean difference is less than zero, so the levels of depression have decreased.
00:31
For part b, identifying the appropriate statistical test, we'll want to do this as a paired or dependent samples t -test.
00:42
For part c, finding the test statistic will be equal to our sample mean, or pardon me, sample mean difference divided by our sample standard deviation of differences over the square root of the sample size.
00:58
We have that d -bar, the sample mean difference, is negative four.
01:04
The standard deviation of differences would be the square root of the variance, so it's going to be 8.
01:11
We have a sample of size 20...