Statistics
posted by Anonymous .
On standard IQ tests, the mean is 100 and the standard deviation is 13. The results are very close to fitting a normal curve. Suppose an IQ test is given to a very large group of people. Find the percent of people whose IQ score is between 61 and 139.

First of all, on standard IQ tests (e.g., WISC and WAIS), SD = 15, but I will go with your data.
Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion between the two Z scores. Change to percentage. 
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