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. Here are the mpg values for a random sample of 20 of these records:

44.3 48.7 45.7 44.1 47.6 38.6 42.4 45.1 38.4 37.8

48.4 35.2 40.3 44.1 43.0 47.2 51.7 49.1 45.9 44.3

(a) Describe the distribution using graphical methods. Is it appropriate to analyze these data using methods based on Normal distributions? Explain why or why not.

(b) Find the mean. (Round your answer to two decimal places.)

Find the standard deviation. (Round your answer to four decimal places.)

Find the standard error. (Round your answer to four decimal places.)

Find the margin of error for 95% confidence. (Round your answer to four decimal places.)

(c) Report the 95% confidence interval for, the mean mpg for this vehicle based on these data. (Round your answers to four decimal places.) (_____mpg, _____mpg)