A new study shows that the death rate on rural roads is higher than that on other roads in the United States. The table that follows is an excerpt taken from “Death rates higher on rural road” in the March 3, 2005, USA Today, which gives the death rates for each state on rural, noninterstate roads in 2003 for every 100 million miles of travel and the rates for all other roads in the state.

State Rural Roads All Others AL 2.45 1.21 AK 1.76 2.00

••• Remainder of data on Student’s Suite CD-ROM.

Source: USA Today

a. Calculate the correlation coefficient and use it and Table 10 to determine a 95% confidence interval for .

b. What other factors could be having an effect on this relationship? Explain.