A college placement office conducted a survey of 100 engineers who had graduated from Stanford University. For these engineers, the mean salary was computed to be $72,000 with a standard deviation of $8,000. The percentage of these engineers who earn more than $96,000 or less than $48,000 is:
A) approximately 0%
B) at least 5.6% (1/18 of the engineers)
C) at most 5.6% (1/18 of the engineers)
D) at most 11.1% (1/9 of the engineers)
E) at least 11.1% (1/9 of the engineers)

Question

Quizplus · Accepted Answer

The standard deviation is $8,000. So, $96,000 is 3 standard deviations above the mean, and $48,000 is 3 standard deviations below the mean. According to the empirical rule, about 99.7% of the data falls within 3 standard deviations of the mean. Therefore, at most 11.1% (1/9 of the engineers) earn more than $96,000 or less than $48,000.

A College Placement Office Conducted a Survey of 100 Engineers