Question

A certain standardized test's math scores have a bell-shaped distribution with a mean of 520 and a standard deviation of 119.

What percentage of standardized test scores is between 401 and 639?
__%

(Round to one decimal place as needed.)

Answer 1

68.3%

Explanation:

You want the percentage of standardized test scores between 401 and 639 if they have a normal distribution with a mean of 520 and a standard deviation of 119.

One standard deviation

The desired range of scores is ±1 standard deviation from the mean:

520 -119 = 401

520 +119 = 639

The empirical rule says the normal distribution has about 68% of its values within 1 standard deviation. The attached calculator output tells us the more precise number is 68.3%.