00:01
For this exercise, we are told that we have a sample of 49 subjects who were treated with some process, and their cholesterol levels were measured before and after treatment.
00:14
The mean difference in their cholesterol levels was 3 .3, and the standard deviation of the difference in levels was 18 .6.
00:24
And here we are asked to construct a 95 % confidence interval estimate of the mean net change.
00:31
So what's been described here is paired samples, where we have a set of.
00:35
Sample where we have a before and an after and we're looking at the difference.
00:42
Now a confidence interval for the situation for the mean difference is given by this formula.
01:20
Now we have the difference mean.
01:23
We have the sample size.
01:26
That's 49.
01:27
We should actually call that n.
01:35
And so we must find this percentile.
01:41
We also have the sample standard deviation of differences...