00:01
Automobile repair costs continue to rise with the average cost now at $367 per repair.
00:17
Assume that the cost for an automobile repair is normally distributed with the standard deviation of $88.
00:25
Answer the following questions about the cost of automobile repairs.
00:29
So the first question is, what's the probability that the mean will be greater than 450? so let's take one minus the probability that z is less.
00:44
Than 450 minus 367 divided by our standard deviation of 88.
00:52
So that's going to give us one minus the probability that z is less than .94.
00:57
.94 corresponds to .8264.
01:01
So we get a probability of .1736.
01:10
So part b, i'm going to make this a little bit smaller.
01:16
What's the probability the cost will be less than $250? so the probability that our mean is less than $250.
01:25
Is the probability that z is less than 250 minus 367 divided by 88.
01:33
Probability that z is less than negative 1 .33 corresponds with probability 0 .0918.
01:43
For part c, what's the probability that the cost will be between 250 and 450? so we're finding the probability that we are between our values.
02:01
Now this one's kind of an interesting one to think about.
02:05
One of the things i want you to remember, so if we look here, we can do the probability.
02:11
We know that 250 has a z value of 1 .33, and 450 has a z value of 0 .94...