00:01
So we want to construct a 99 % confidence interval for this data here.
00:06
We have kids who learn to read by age 4 and after age 4, and whether they were read to three or more times a week, or of course whether they were read to fewer than three times a week.
00:22
And we want to construct that confidence interval for a difference of proportions.
00:27
And this is the formula i have here in black.
00:30
So the first thing we need to do is find our two point estimates, p1 and p2.
00:35
So i'm going to let p hat 1 be the column where the kids have read to at least three times a week.
00:44
And kids who learn to read by age 4, it would be 47 divided by the sum, which is 77.
00:54
And that equals 0 .60 .6104.
01:07
And our second point estimate for the kids who are not read to three or more times a week, it would be 30 over 62 plus 30 or 92, which is equal to 0 .3261.
01:27
Now, this is a 99 % confidence interval, our z value is going to be 2 .58.
01:36
Now we just need to calculate the standard error here...