00:01
Okay, here we have two independent random samples.
00:03
So n1 is 578 and n2 is 593.
00:15
And then we have their proportions.
00:18
So p1 is going to be 0 .59 and p2 is going to be 0 .68.
00:28
And we want to come up with a 90 % confidence interval for the true difference between the population proportions.
00:36
So what we're going to do is the formula is just going to be p1 minus p2.
00:41
So i'll just type that in right now, 0 .59 minus 0 .68.
00:49
So we get negative 0 .09 plus and minus z times the square root of p hat.
01:07
Oops, sorry, hang on.
01:08
It's just going to be p1 hat times 1 minus p1 hat over n1 plus p2 hat times 1 minus p2 hat over n2.
01:27
So to figure out the z, that just depends on the 90 % confidence interval.
01:34
So it's like totally dependent on the confidence interval that you choose.
01:37
All you need to do is look up 90 % confidence interval z score.
01:42
And this is just a known value.
01:44
It's going to be on any z chart that you have.
01:46
So 0 .09 plus and minus.
01:48
So at 90%, z is 1 .645 square root.
01:55
And then it's going to be 0 .59 times 1 minus 0 .59...