Question

In an English course, students had to turn in a final paper. The mean grade earned by the class was 74.9 with a standard deviation of 3.1 points. The scores are approximately bell-shaped. Approximately 68% of all final paper scores were between two values A and B. What is the value of A? Write only a number as your answer

Answer 1

Solution :

Given that,

mean = = 74.9

standard deviation = = 3.1

Using Empirical rule,

P( - < x <   + ) = 68%

= P( 74.9 - 3.1 < x < 74.9 + 3.1 ) = 68%

= P( 71.8 < x < 78.0 ) =68%

A = 71.8

B = 78.0