00:01
In a recent year, the total scores for certain standardized tests are normally distributed with a mean of 500 and a standard deviation of 10 .3.
00:12
Find the probability that a randomly selected medical student who took the test had a total score that was less than 494.
00:22
So a probability that x is less than 494 is calculated by doing the probability that z is less than 494 minus our mu of 500.
00:33
Divided by our standard deviation of 10 .3.
00:38
So that gives us a z score of negative 0 .58, which corresponds to a probability of 0 .2810 when we look it up in our standard normal table.
00:50
For part b, now we're going to find the probability that a randomly selected medical student who took the test had a score that was between 498 and 513.
01:03
So 498 is less than x, which is less.
01:06
Than 513.
01:09
So we'll take 498 minus 500 divided by 10 .3 is less than z, which is less than 513 minus 500 divided by 10 .3.
01:22
So that's going to put z in between negative 0 .19 and 1 .26.
01:31
So 1 .26 corresponds to 0 .8962 and from that we'll subtract.
01:37
The probability that corresponds to negative .19, which is .427...