The report “Older Driver Involvement in Injury Crashes in Texas” (Texas Transportation Institute, 2004) included a scatterplot of y fatality rate

(percentage of drivers killed in injury crashes) versus x driver age. The accompanying data are approximate values read from the scatterplot.

Age Fatality Rate Age Fatality Rate 40 10.86

a. Construct a scatterplot of the data. What characteristics of the plot suggest that a cubic regression would be m 1.15 90 3.20 65 1.20

a. Construct a scatterplot of these data.

b. Using Table 5.5 and the ladder of transformations in Figure 5.38, suggest a transformation that might result in variables for which the scatterplot would exhibit a pattern that was more nearly linear.

c. Reexpress x and/or y using the transformation you recommended in Part (b). Construct a scatterplot of the transformed data.

d. Does the scatterplot in Part

(c) suggest that the transformation was successful in straightening the plot?

e. Using the transformed variables, fit the least-squares line and use it to predict the fatality rate for 78-yearold drivers. 1.893