I am drawing a blank on how to solve this problem. Can somebody help?

"A normal distribution consist of 100 scores with a mean of 65 and a standard deviation of 5. How many scores are above 70 and how many are below 55? :confused:

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- June 17th 2007, 11:51 AMgraceofayakNormal distribution
I am drawing a blank on how to solve this problem. Can somebody help?

"A normal distribution consist of 100 scores with a mean of 65 and a standard deviation of 5. How many scores are above 70 and how many are below 55? :confused: - June 17th 2007, 12:03 PMCaptainBlack
Badly posed question, the scores may have a normal distribution with mean

65 and SD of 5, but the numbers above 70 and below 55 are random

variables, and so not fixed numbers. We can talk of the percentage of scores

above 70 and below 55, but these will not be the number out of a sample of

100 that are above and below these values (well not often anyway).

RonL

(70 is 1 SD above the mean so looking 1 up in a table of the standard normal

distribution we find 84.13% of scores are below 70, and so 15.87% are above

70. Similarly 55 is 2 SD's below the mean so looking -2 up in the table of the

cumulative standard normal distribution we see that 2.28% of scores are less

than 55.)