00:01
We've been given some data from a survey of 1 ,006 people.
00:06
So our sample size, n, is 1 ,0006.
00:10
And out of this, 86 % didn't believe in reality tv.
00:16
So p -hap is 0 .86, our sample proportion.
00:21
We want to make a 95 % confidence interval.
00:25
We want to find what the error would be.
00:27
Okay.
00:28
So we have a binomial experiment, either they fell into the group we're looking at, or they said something else.
00:37
And we have a very large sample size.
00:39
So it's safe to use a normal approximation here.
00:43
And when you can use a normal approximation for the binomial, this is a formula for your confidence interval.
00:49
P hat plus or minus your margin of error.
00:53
So that would be z root p hat, 1 minus pheap.
01:00
Over n.
01:03
So we have p hat, we have n, we just need z, and we get back from our level of confidence.
01:08
It's going back to our normal approximation...