Refer to Chapter 9, Review Exercise 18. In the study cited in that exercise, Maria Mathias (A-13)

investigated the relationship between ages (AGE) of boys and improvement in measures of hyperactivity, attitude, and social behavior. In the study, subjects were randomly assigned to two different treatments. The control group (TREAT ) received standard therapy for hyperactivity, and the treatment group (TREAT ) received standard therapy plus pet therapy. The results are shown in the following table. Create a scatter plot with age as the independent variable and ATT

(change in attitude with positive numbers indicating positive change in attitude) as the dependent variable. Use different symbols for the two different treatment groups. Use multiple regression techniques to determine whether age, treatment, or the interaction are useful in predicting ATT.

Report your results.

Subject TREAT AGE ATT Subject TREAT AGE ATT 1 1 9 17 0 10 0.4 2 1 9 0.0 18 0 7 0.0 3 1 13 19 0 12 1.1 4 1 6 20 0 9 0.2 5 1 9 1.0 21 0 7 0.4 6 1 8 0.8 22 0 6 0.0 7 1 8 23 1 11 0.6 8 1 9 24 1 11 0.4 9 0 7 0.0 25 1 11 1.0 10 0 12 0.4 26 1 11 0.8 11 0 9 27 1 11 1.2 12 0 10 1.0 28 1 11 0.2 13 0 12 1.4 29 1 11 0.8 14 0 9 1.0 30 1 8 0.0 15 0 12 0.8 31 1 9 0.4 16 0 9 1.0 Source: Maria Mathias, M.D. and the Wright State University Statistical Consulting Center. Used with permission.

For each study described in Exercises 19 through 21, answer as many of the following questions as possible:

(a) Which is the dependent variable?

(b) What are the independent variables?

(c) What are the appropriate null and alternative hypotheses?

(d) Which null hypotheses do you think were rejected? Why?

(e) Which is the more relevant objective, prediction or estimation, or are the two equally relevant?

Explain your answer.

(f) What is the sampled population?
(g) What is the target population?
(h) Which variables are related to which other variables? Are the relationships direct or inverse?
(i) Write out the regression equation using appropriate numbers for parameter estimates.
( j) Give numerical values for any other statistics that you can.
(k) Identify each variable as to whether it is quantitative or qualitative.
(l) Explain the meaning of any statistics for which numerical values are given.