00:03
All right, so we're told we've got a normal distribution, mean 25, standard deviation of four.
00:07
And then we're going to take a sample of size 25 from that population.
00:10
And we want to find the probability that our sample mean is greater than 23.
00:15
Okay, so the mean is still going to be 25, but the standard deviation, since i'm taking samples of size 25, is four over the square of 25, which is going to be four -fits.
00:26
Okay, or 0 .8.
00:28
So using normal cdf, lower amount 23.
00:33
Up around a really, really, really large number.
00:36
Mean 25, standard deviation of 0 .8.
00:38
This gives us a probability of 0 .9938.
00:44
And then using that same information with a mean of 25 and a standard deviation of 0 .8, we would find the probability that the sample mean is less than some value is 0 .81 or 81%...