Question

Suppose you buy a new car whose advertised mileage is 20 miles per gallon​ (mpg). After driving your car for several​ months, you find that its mileage is 15.7 mpg. You telephone the manufacturer and learn that the standard deviation of gas mileages for all cars of the model you bought is 1.26 mpg. Find the​ z-score for the gas mileage of your​ car.

Answer 1

`(15,7 - 20)/(1,26) = - 3,4`

Explanation:

To determine the Z - score, it is calculated as follows:

`(X - X_(avg) )/(σ)`

Then:

`(15,7 - 20)/(1,26) = - 3,4`

It means that there are more than 3 standar deviations below the advertised mileage.