00:03
Alrighty, so we have a good little sample size question here.
00:11
We want to figure out the daily rainfall amounts in boston we need to have a 99 % confidence level that the sample mean is within 0 .01 inches of the population mean.
00:28
And we're given this population standard deviation.
00:31
So we're going to use this formula here and equals the z.
00:37
At the confidence interval.
00:40
We'll do c -i here.
00:43
We square that, and then we multiply it by sigma, which is the population standard deviation times the complement of that all over the margin of error squared.
01:02
I'll just write m .e for margin of error.
01:04
So we're given lots of these things.
01:06
So the confidence level is 0 .99.
01:09
So the z score that corresponds to that is 2 .36.
01:15
And we're going to square that.
01:18
Multiply that by big dot for multiply sigma, which is, here we go, 0 .212.
01:29
You know what, let me use parentheses.
01:30
It's just a little prettier.
01:33
Times a complement all over the margin of error we want...