Interpret the values 62, 32.8, 41.3, and 7.8 in the upper left cell of the cross tabulation.

Med. 3.63 The correlations computed for the six variables in the epilepsy study are given here. Do the sizes of the correlation coefficients reflect the relationships displayed in the graphs given in Exercise 3.62? Explain your answer. Placebo Group Y 1 Y 2 Y 3 Y 4 Base Y 2 .782 Y 3 .507 .661 Y 4 .675 .780 .676 Base .744 .831 .493 .818 Age .326 .108 .113 .117 .033 Treatment Group Y 1 Y 2 Y 3 Y 4 Base Y 2 .907 Y 3 .912 .925 Y 4 .971 .947 .952 Base .854 .845 .834 .876 Age ⫺ .141 ⫺ .243 ⫺ .194 ⫺ .197 ⫺ .343 Med. 3.64 An examination of the scatterplots reveals one patient with a very large value for baseline count and all subsequent counts. The patient has ID 207.

a. Predict the effect of removing the patient with ID 207 from the data set on the size of

the correlations in the treatment group.

b. Using a computer program, compute the correlations with patient ID 207 removed

from the data. Do the values confirm your predictions? Med. 3.65 Refer to the research study concerning the effect of social factors on reading and math scores. We justified studying just the reading scores because there was a strong correlation be- tween reading and math scores. Construct the same plots for the math scores as were constructed for the reading scores.

a. Is there support for the same conclusions for the math scores as obtained for the read-

ing scores? b. If the conclusions are different, why do you suppose this has happened? Med. 3.66 In the research study concerning the effect of social factors on reading and math scores, we found a strong negative correlation between minority and poverty and reading scores.

a. Why is it not possible to conclude that large relative values for minority and

poverty in a school results in lower reading scores for children in these social classes?

b. List several variables related to the teachers and students in the schools which may be

important in explaining why low reading scores were strongly associated with schools having large values of minority and poverty. Soc. 3.67 In the January 2004 issue of Consumer Reports an article titled “Cut the fat” described some of the possible problems in the diets of the U.S. public. The following table gives data on the increase in daily calories in the food supply per person. Construct a time-series plot to display the increase in calorie intake. Year 1970 1975 1980 1985 1990 1995 2000 Calories 3,300 3,200 3,300 3,500 3,600 3,700 3,900 a. Describe the trend in calorie intake over the 30 years. b. What would you predict the calorie intake was in 2005? Justify your answer by explaining any assumptions you are making about calorie intake.