If an IQ distribution is normal and has a mean of 100 and a standard deviation of 15, then 99% of all those taking the test scored between IQ's of
A) 0 and 150
B) 55 and 145
C) 85 and 115
D) 92.5 and 107.5

Question

Quizplus · Accepted Answer

In a normal distribution, 99% of the data falls within 2.58 standard deviations of the mean. Calculating 2.58 standard deviations from the mean (100) in both directions with a standard deviation of 15 gives: 100 ± (2.58 * 15) = 100 ± 38.7, which approximates to the range of 61.3 to 138.7. However, among the provided options, option B (55 to 145) is the closest to encompassing 99% of scores, given the options available.

If an IQ Distribution Is Normal and Has a Mean