00:01
Suppose the lengths of pregnancies of a certain animal are approximately normally distributed with a mean of 251 days and a standard deviation of 18 days.
00:11
Part a, what is the probability that a randomly selected pregnancy lasts less than 245 days? so we're finding x is less than 245, which will do the probability that z is less than 245 minus 251 divided by 18.
00:35
That gives us a z value of negative .33, which corresponds to .3707.
00:47
So it looks like you selected out of some choices, a, if 100 pregnant individuals were selected independently from this population, we would expect 37 pregnancies.
00:58
So i agree with that statement.
01:01
So i'm just going to go ahead and put a capital a and circle it.
01:05
And we're going to move on to part b.
01:07
So part b, suppose a random sample of 22 pregnancies is obtained, describe the sampling distribution of the sample mean length of pregnancies.
01:21
So we have n equals 22.
01:26
The sampling mean is going to be 251.
01:30
The sampling standard deviation is found by taking 18 divided by the square root of 22, which which is 3 .8376.
01:48
So for part c, what is the probability that a random sample of 22 pregnancies has a mean gestation period of 245 days or less? so the difference between a and c is this time when we do the probability that z is less than 245 minus 251...