00:01
The following is a solution for number 15, and this looks at private versus public school teachers to see if they have nbc licenses.
00:07
And for private, out of 80, 0 .175 said that they hold this particular license.
00:13
And for public out of the 520, 15 % said that they hold this license.
00:17
So the point estimate for p1 minus p2 is simply just the statistics behind that, which is p1 hat minus p2 hat.
00:26
And that's actually given to us.
00:27
So the p hats are over here.
00:28
So let's just assume that the first is private and the second is public.
00:32
So 0 .175 minus 0 .15, and that's 0 .025.
00:38
Okay, so that's the point estimate.
00:40
Now we find the 90 % confidence interval.
00:43
And if we go to stat and arrow over to test and then go over to the b option to prop zint, and we can type in our data.
00:51
Oh, i forgot to show you this.
00:53
So the x and the x1, x2, we actually need to find that.
00:58
So the way you find that, and i'll do it up here.
01:00
So x1, it's just the end, the sample size, times the p hat.
01:05
So if we take 80 times 0 .175, you should get 14.
01:09
And then if you take 520 times 0 .15, you should get 78.
01:13
So those are your favorable, the number favorable.
01:16
So they give us the proportion here, and we needed the number here to use the calculator.
01:21
So 14 out of the 80 should give you that 0 .175.
01:25
And then 78 out of 520 should give you that .15.
01:29
And we want to be 90 % confident, so 0 .9...