In a study of 82 video game players, the researchers found that the ages of these players were normally distributed, with a mean age of 17 years and a standard deviation of 3 years. determine the likely number of possible players in this study over the age of 20.
a. 15
b. 20
c. 14
d. 13

The normal distribution of this problem is shown below

We first need to standardise the value of X=20



Reading from the z-table, the probability of z-score 1 is 0.8413

This reading is for the area to the left of z=1.
The area to the right of z=1 is then 1-0.8413=0.1387
The probability of player over 20 years of age is 0.1387
Of 82 video game players, there is a possibility of 0.1387×82=13 possible player