Question

The air pressure of each tire in a group is normally distributed with a mean of 39.2 pounds per square inch (psi) and a standard deviation of 2.5 . If a tire in this group has a z-score of -1.8, find its air pressure.

Answer 1

The air pressure corresponding to that z-score is 34.7 psi

Explanation:

Mathematically, z-score can be calculated using the formula;

z-score = (x-mean)/SD

from the w, we identify the following;

z-score = -1.8 , x = ? , mean = 39.2 psi and SD (standard deviation) = 2.5

Plugging these values, we have;

-1.8 = (x-39.2)/2.5

2.5 * -1.8 = x -39.2

-4.5 = x -39.2

x = 39.2 - 4.5

x = 34.7 psi