Fuel efficiency Computers in some vehicles calculate various

Fuel efficiency. Computers in some vehicles calculate various quantities related to performance. One of these is the fuel efficiency, or gas mileage, usually expressed as miles per gallon (mpg). For one vehicle equipped in this way, the mpg were recorded each time the gas tank was filled, and the computer was then reset.¹³ Here are the mpg values for a random sample of 20 of these records:

Suppose that the standard deviation is known to be ? = 3.5 mpg.

(b) Examine the data for skewness and other signs of non-Normality. Show your plots and numerical summaries. Do you think it is reasonable to construct a confidence interval based on the Normal distribution? Explain your answer. (Use Minitab)

(c) Give a 95% confidence interval for ?, the mean mpg for this vehicle. (Use Minitab)

1.5 50.7 36.6 37.334.2 45.0 48.0 43.2 47.742.2 43.2 44.6 48.4 46.4 46.8 39.2 37.3 43.5 44.3 43.3

Solution