The time for a professor to grade an exam is normally distributed with a mean of 16.3 minutes and a standard deviation of 4.2 minutes. The interval around the mean that contains 68% of the times needed to grade exams is------ .

Question

Quizplus · Accepted Answer

The interval that contains 68% of the times is one standard deviation away from the mean in both directions. Therefore, subtracting and adding the standard deviation (4.2 minutes) from the mean (16.3 minutes) gives us 12.1 to 20.5 minutes.

The Time for a Professor to Grade an Exam Is