00:01
Here we want to find the probability that for an adult after 12 hours of fasting, x is going to be more than 60, less than 110, between 60 and 110, and then greater than 125.
00:30
We have that this is approximately normal with a mean of 80 and a standard deviation of 27.
00:46
And because we know the population standard deviation, we can do a z -score.
00:50
So i'm going to do z equals 60 minus 80 over 27, z equals 110, oops, minus 80 over 27, and z equals 125 minus 80 over 27.
01:22
And i'm going to calculate these z -scores.
01:24
So we're just going to type this in the calculator.
01:27
60 minus 80 divided by 27 is negative 0 .74.
01:32
110 minus 80 is 30 divided by 27 is 1 .11.
01:42
Then 125 minus 80 divided by 27 is 1 .67.
01:52
We're going to find the probabilities now.
01:56
So i'm going to need to put in a z -chart real quick.
01:58
So i'm going to bring this down.
02:08
I'm also going to make it smaller so that we can see both sides of the chart.
02:13
So let's go back up to part a.
02:18
I want to find the probability that x is greater than 60.
02:21
That's equivalent to finding the probability that z is greater than negative 0 .74.
02:28
So i'm going to go down to the chart and look for negative 0 .74.
02:35
So negative 0 .701234 .2296.
02:45
And charts give you probability of less than.
02:48
So if you need greater than, you have to do 1 minus that...