00:01
Hello, welcome to this lesson.
00:03
In this lesson we are looking at 91 % confidence interval for the difference between the means of the two populations.
00:12
So we have the first sample, we have the mean as 31, the sample size as 75 and the standard deviation as 5.
00:22
The second sample we have the mean as 24, the sample size as 69 and the standard deviation as 2.
00:32
So we would need the point estimate, the point estimate for the difference of the means.
00:47
So the point estimate would be the mean 1 minus the mean 2.
00:54
So the difference between the means would have mean 1 which is 31 minus the mean 2 which is 24.
01:09
So we have 31 minus 24 and that is 7.
01:16
The second step is that we would need the margin of error for us to construct the confidence interval.
01:25
So margin of error, the margin of error is giving us the z -score times the square root of the standard deviation of sample 1 squared all along the sample size and plus the standard deviation of sample 2 squared all on the sample size 2.
02:02
So for confidence level of 91 % it corresponds with a z -score of 1 .68.
02:11
Okay, at this point the margin of error would be close to 1 .68 times the square root of, we have the sample size.
02:27
Let's deal with the standard deviation first.
02:29
So we have the standard deviation of sample 1 as 5.
02:34
We square that.
02:36
We divide by the sample size of sample 1 which is 75...