Question

The GMAC Insurance company reported that the mean score on the National Drivers Test was 78.9 with a standard deviation of 2.9 points. The test scores are approximately bell-shaped. Approximately 68% of all test scores were between two values A and B. What is the value of A? Write only a number as your answer. Round to one decimal place.

Answer 1

Solution :

Given that,

mean = = 78.9

standard deviation = = 2.9

Using Empirical rule,

a) P( - < x <   + ) = 68%

= P( 78.9- 2.9 < x < 78.9 + 2.9) = 68%

= P( 76 < x < 81.8 ) = 68%

A =76

B = 81.8