Use of the Internet and a long life. Exercise 4.20 (page 168) asks the question "Will you live longer if you use the Internet?" Figure 4.9 (page 168) is a scatterplot of life expectancy in years versus number of Internet users for 181 countries. The scatterplot shows a positive association between these two variables. Do you think that this plot indicates that Internet use causes people to live longer? Give another possible explanation for why these two variables are positively associated.
(a) Describe the relationship between these two variables.
(b) A friend looks at this plot and concludes that using the Internet will increase the length of your life. Write a short paragraph explaining why the association seen in the scatterplot does not provide a reason to draw this conclusion.