The city and highway gas mileages (in miles per gallon) of all cars are described by the histograms in Fig 142 and Fig 143, respectively.
Fig. 142

Fig. 143

a. Describe the shapes of the distributions.
b. Compare the spreads of the distributions. What does your comparison mean in this situation?
c. For city gas mileages, which class contains the 50th percentile? For highway gas mileages, which class contains the 50th percentile?
d. Use the results you found in part (c) to help you estimate the difference of the 50th percentile for highway gas mileages and the 50th percentile for city gas mileages. What does it mean in this situation?
e. The city and highway gas mileages of all cars are de- scribed by just one histogram in Fig. 144. Explain why the distribution is unimodal even though the 50th percentiles for the city distribution and the highway distribution are quite different.
Fig. 144

f. Explain why your response to part (e) suggests that a population with a unimodal distribution may consist of two or more subgroups that are quite different.

Transcribed Image Text:

City Gas Mileages 0.4 0.38 0.3 0.27 eoe 0.2 0.15 0.15 0.1 0.03 0.01 0.01 5 10 15 20 25 30 35 40 45 50 55 Miles per gallon Highway Gas Mileages 0.4 0.3 0.3 0.23 0.2 0.2 0.12 0.11 0.1 0.04 0.01 0.01 5 10 5 20 25 30 35 40 45 50 Miles per gallon Both City and Highway Gas Mileages 0.24 0.25 0.25 6 0.2 0.15 0.1 0.05 0.22 0.11 0.08 0.06 0.02 0.01 5 10 15 20 25 30 35 40 45 50 55 Miles per gallon