2.29 Try a log. Refer to the previous exercise. INBIRTH 40 (a) Make a scatterplot of the log of births per 1000 people versus Internet users per 100 people. 30 - (b) Describe the relationship that you see in this plot and compare it with Figure 2.11. 20 - (c) Which plot do you prefer? Give reasons for your answer. 10 - 2.30 Make another plot. Refer to Exercise 2.28. INBIRTH (a) Make a new data set that has Internet users expressed as users per 10,000 people and births as births per 10,000 people. 1 2 4 6. 7 8 9 10 11 12 Percent alcohol FIGURE 2.10 Scatterplot of carbohydrates versus percent alcohol for 153 brands of beer, for Exercise 2.26. (b) Explain why these transformations to give new variables are linear transformations. (Hint: See linear transformations on page 45.) 2.27 More beer. Refer to the previous exercise. BEER (c) Make a scatterplot using the transformed variables. (a) Make a scatterplot of calories versus percent alcohol using the data set without the outlier. (d) Compare your new plot with the one in Figure 2.11. (e) Why do you think that the analysts at the World Bank chose to express births as births per 1000 people and Internet users as users per 100 people? (b) Describe the relationship between these two variables. 2.28 Internet use and babies. The World Bank collects data on many variables related to world development for countries throughout the world. Two of these are Internet use, in number of users per 100 people, and birthrate, in births per 1000 people.13 Figure 2.11 is a scatterplot of birthrate versus Internet use for the 106 countries that 2.31 Explanatory and response variables. In each of the following situations, is it more reasonable to simply explore the relationship between the two variables or to view one of the variables as an explanatory variable and the other as a response variable? In the latter case, which is the explanatory variable and which is the response variable? have data available for both variables. 1 INBIRTH (a) Describe the relationship between these two variables. (a) The reading ability of a child and the shoe size of the child. (b) A friend looks at this plot and concludes that using the Internet will decrease the number of babies born. Write a short paragraph explaining why the association seen in the scatterplot does not provide a reason to draw this conclusion. (b) College grade point average and high school grade point average. (c) The rental price of an apartment and the number of square feet in the apartment. 50 (d) The amount of sugar added to a cup of coffee and how sweet the coffee tastes. 40 (e) The temperature outside today at noon and the temperature outside yesterday at noon. 30 2.32 Parents' income and student loans. How well 20 does the income of a college student's parents predict how much the student will borrow to pay for college? We have data on parents' income and college debt for a sample of 1200 recent college graduates. What are the explanatory and response variables? Are these variables 90 8. 10 - 50 60 70 80 categorical or quantitative? Do you expect a positive or negative association between these variables? Why? 10 20 30 40 Internet users per 100 people FIGURE 2.11 Scatterplot of births (per 1000 people) versus Internet users (per 100 people) for 106 countries, for 2.33 Reading ability and IQ. A study of reading ability in schoolchildren chose 60 fifth-grade children at random from a school. The researchers had the children's scores Exercise 2.28. Births per 1000 people Carbohydrates (g)