Question

At the U.S. Open Tennis Championship a statistician keeps track of every serve that a player hits during the tournament. The statistician reported that the mean serve speed of a particular player was 103 miles per hour (mph) and the standard deviation of the serve speeds was 11 mph.Assume that the statistician also gave us the information that the distribution of serve speeds was mound-shaped and symmetric. What percentage of the player's serves were between 115 mph and 145 mph?
A) approximately 16%
B) at most 34%
C) at most 2.5%
D) at most 13.5%

Answer 1

Answer:

D

Step-by-step explanation:

What we need to do here is to calculate the required probability and convert to percentage

Firstly, we start by calculating the z-scores of the two boundary limits

Mathematically;

z-score = (x-mean)/SD

Form the question, we can see that the mean is 103 and the standard deviation is 11

so for 115, z-score would be

z-score = (115-103)/11 = 1.1

For 145, z-score would be

(145-103)/11 = 3.8

So the probability we want to calculate would be;

P(1.1<z<3.8)

We use the standard normal table for this

Mathematically;

P(1.1<z<3.8) = P(z<3.8) - P(z<1.1) = 0.13559

which to percentage is 13.559 %

The closest answer here is D