00:01
So with a mean of 52 .25, and n being 20, and our standard deviation being 56.
00:11
For a, we'll have to find a confidence interval for the 90%, 95%, and 99th percent.
00:18
So for the 90%, we're gonna have 52 .25, plus or minus the z here is gonna be 1 .645.
00:32
We can look at the table for that one.
00:33
And then times 56 over the square root of 20.
00:39
Toss that into a calculator, and we'll end up with 5204 .4, and then 5245 .59.
00:57
For the 95th percentile confidence interval, that's 52 .25 plus or minus our z here is gonna be 1 .96 times 56 over the square root of 20.
01:15
So that's 5200 .45, and then 5249 .54.
01:32
And then for the 99th, or 99th percent confidence interval, we're gonna have 52 .25 plus or minus our z here is gonna be 2 .576 times 56 over the square root of 20.
01:52
And we'll end up with a confidence interval of 5192 .4.
02:03
And 52 .27 .25.
02:09
For b, we want to find the third quartile in the 70th percentile.
02:19
So the third quartile is 75%.
02:21
So 75%, that's gonna have our z value to be 0 .6745...