Scores of adults aged 60 to 64 on a common IQ test are approximately Normally distributed with mean 90 and standard deviation 15.
What range of IQ scores contains the central 95% of the population of adults aged 60 to 64?
A) 75 to 105
B) 60 to 120
C) 30 to 150
D) 45 to 135

Question

Quizplus · Accepted Answer

The central 95% of a normal distribution is covered by ±2 standard deviations from the mean. With a mean of 90 and a standard deviation of 15, 2 standard deviations is 30. Therefore, 90 ± 30 = 60 to 120.

Scores of Adults Aged 60 to 64 on a Common