Question

IQ scores for adults age 20 to 34 years are normally distributed according to N(120, 20). In what range does the middle 68% of people in this group score on the test?

100−140
120−160
80−120
80−140
120−160

Answer 1

100−140

Step-by-step explanation:

The normal distribution has two parameters:

The mean
`\mu`

The standard deviation
`\sigma`.

It can be called
`N(\mu, \sigma)`.

The 68-95-99.7 rule indicates that:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviations of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

N(120,20).

This means that the middle 68% of people in this group score on the test are in the range of 120-20 = 100 to 120+20 = 140.