The speeds of the fastballs thrown by major league baseball pitchers were measured by radar gun. The mean speed was 87 miles per hour. The standard deviation of the speeds was 3 mph. Which of the following speeds would be classified as an outlier?
A) 97 mph
B) 81 mph
C) 92 mph
D) 84 mph

Question

Quizplus · Accepted Answer

An outlier is typically defined as a value that is more than 2 standard deviations away from the mean. Here, 2 standard deviations from the mean (87 mph) is 6 mph (2 * 3 mph). Therefore, speeds less than 81 mph or greater than 93 mph would be considered outliers. 97 mph is more than 93 mph, so it is an outlier.

The Speeds of the Fastballs Thrown by Major League Baseball