Exercise 7.17 used regression to predict a post-intervention score based on pre-intervention score and a particular intervention. The following table shows a model incorporating interaction between pre-intervention score and intervention.

(a) Write the model equation.

(b) Interpret the model coefficients.

(c) Write a separate model equation for each intervention group.

(d) Do these data suggest that there is a statistically significant difference in association between pre- and post-intervention scores by treatment group? Explain your answer.

Data From Exercise 7.17

Data From Exercise 7.15

Data From Exercise 5.35

Data From Exercise 5.47

   

Estimate Std. Error t value Pr(>|t) (Intercept) -17.5790 17.7090 -0.99 0.3275 pre treatment Neutral 1.2813 67.7518 0.2376 5.39 0.0000 30.6168 2.21 0.0333 treatment Therapeutic 64.4183 24.2124 2.66 0.0116 pre:treatmentNeutral -0.9890 0.4082 -2.42 0.0206 pre:treatment Therapeutic -1.0080 0.3266 -3.09 0.0039