As a result of government and consumer pressure, automobile manufacturers in the United States are deeply involved in research to improve their products' gasoline mileage. One manufacturer, hoping to achieve 40 miles per gallon on one of its compact models, measured the mileage obtained by 36 test versions of the model with the following results (rounded to the nearest mile for convenience):

The mean and standard deviation of these data are shown in the SAS printout below.

a. Find the mean and standard deviation on the printout and give the units in which they are expressed.

b. If the manufacturer would be satisfied with a (population) mean of 40 miles per gallon, how would it react to the above test data'?

c. Use the information in Tables 2.8-2.9 to check the reasonableness of the calculated standard deviation s = 2.2.

d. Construct a relative frequency histogram of the data set. Is thc data set mound-shaped?

e. What percentage of the measurements would you expect to find within the intervals i f s, T f 2s, x i 3s?

f. Count the number of measurements that actually fall within the intervals of part

e. Express each interval count as a percentage of the total number of nieasurements. Compare thesc results with your answers to part e.