4.

(a) The following are results of fuel economy tests (miles per gallon) obtained from a sample of 50 automobiles in 1975:

Plot the histogram of these data and calculate the sample average and sample standard deviation.

(b) The following 50 results were obtained in 1985:

Plot the histogram of these data and calculate the sample average and sample standard deviation. Considering both data sets, comment on any interesting aspects you find. Make a list of questions you would like answered that would allow you to investigate further.

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17.74 12.17 12.22 13.89 16.47 15.88 16.10 16.74 17.54 17.43 14.57 12.90 12.81 14.95 16.25 17.13 14.46 14.20 16.90 11.34 12.57 13.15 16.53 13.60 13.34 13.67 14.23 15.81 16.63 11.40 14.94 13.66 9.79 13.08 14.57 14.93 14.01 14.43 16.35 15.65 11.52 17.46 14.67 15.92 16.02 13.46 13.70 13.70 14.98 14.57 15.72