00:01
To solve this problem, first we want to find a z score for the value 90.
00:06
So z score for value 9.
00:09
It's going to regard to the x value minus the mean over standard deviation, which is equal to 19 minus 20 over 30 which is equal to negative 1.
00:23
So to visualize that on the normal distribution, now we go over distribution.
00:31
The negative one should be right here.
00:35
And what to find the area to the right of it.
00:39
Sorry, to the left of it.
00:40
And that's going to be our probability.
00:43
So to do that, you can use a z table, or you can use a t -80 for roughing calculator.
00:54
So if you use a t -a -4 roughing calculator, here is the formula you use.
00:59
The function lovable cdm of negative e99 to negative 1, 0 ,000...