Question

Suppose the number of gallons of gasoline per day used by a car is normally distributed with a mean of 2.2 gallons and a standard deviation of 1.2 gallons.

What is the difference in gallons per day used by a car with a z-score of 3 and another car that has a z-score of 0?


1.2
2.6
3.6
4.6

Answer 1

The z-score counts the number of standard deviations from the mean. Then the meaning in gallons of a difference in z-score is found by multiplying the z-score difference by the value of a standard deviation.

(3 -0)*1.2 = 3.6 . . . . gallons.

The 3rd selection is appropriate.