solution

Aircraft. Look again at Display 3.76 on page 174, which shows a scatterplot of flight length versus number of seats.

a. Does the slope of the pattern increase, decrease, or stay roughly constant as you move from left to right across the plot?

b. Focusing on the variation (spread) in flight length, y, for planes with roughly the same seating capacity, compare the spreads for planes with few seats, a moderate number of seats, and a large number of seats. As you move from left to right across the plot, how does the spread change, if at all?

c. Suppose a friend chose a plane from the sample at random and told you the approximate number of seats. Could you guess its flight length to within 500 miles if the number of seats was between 50 and 150? If it was between 200 and 300? Explain.

d. What is the relationship between your answer in part b and residual plot I in Display 3.77?

e. Give an explanation for why the variation in flight length shows the pattern it does.