00:01
All right, so here we have a normal distribution, and we know that the probability of being less than 40 is 0 .25, and we know the standard deviation is 50.
00:13
So what i'm going to do is i'm going to figure out what the z score is for that.
00:17
We know the z score, 0, 1, i'll put negative 2, negative 1, negative 3, 1, 2, and 3 in terms of our z score.
00:32
So, and that is at the 25th percentile.
00:34
So it's the q1 of the data set.
00:36
So what i'm going to do is i'm going to do inverse norm, area to the left is 0 .25, 0, and 1.
00:43
I'm going to find the z score for that percentile.
00:47
And then we can use the z score formula to find the mean...