The speed of college tennis player Jaron Jackson's first serve averages 125 mph, with a standard deviation of 4 mph.If the distribution of service speeds is normal, what proportion of Jaron's serves will be less than 136 mph?
A).9970
B).8762
C).8356
D).9721
E).9402

Question

Quizplus · Accepted Answer

The z-score for a serve speed of 136 mph is (136 - 125) / 4 = 2.75. The proportion of serves less than 136 mph is the area under the normal distribution curve to the left of z = 2.75, which is 0.9970.

The Speed of College Tennis Player Jaron Jackson's First Serve