00:02
I've got our picture all set up here, and we need to use this picture and our standard normal probability table to figure out, first of all, the probability of the tax return is going to be more than $3 ,500.
00:14
So we're going to need a z score for $3 ,500.
00:18
So we'll do $3 ,500 minus the mean, divided by the standard deviation, which is going to give us a value of 1 .196, which would be a value.
00:40
Round up to 1 .20.
00:44
So here we are at 1 .20 z score, which is right about here at $3 ,500.
00:50
And now when we look up that z score in our standard normal probability table, 1 .20 gives us a probability to the left of 0 .8849.
01:03
So our probability to the right is going to be equal to 1 minus 0 .8849, which is equal to 0 .1151.
01:20
Now for our next question, we want to know what's the probability between 3 ,500 and 4 ,000.
01:28
So let's get a z score for 4 ,000.
01:36
There's my mean and 4 ,000 minus the mean divided by the standard deviation, which comes out to be 2 .16...