Refer to the Journal of Human Stress study of firefighters, Exercise 12.5. Consider using the qualitative variable, level of social support, as a predictor of emotional stress y. Suppose that four social support levels were studied: none, low, moderate, and high.

a. Write a model for E(y) as a function of social support at four levels.

b. Interpret the β parameters in the model.

c. Explain how to test for differences among the emotional stress means for the four social support levels.

Data from Exercise 12.5

The Journal of Human Stress (Summer 1987) reported on a study of “psychological response of firefighters to a chemical fire.” The researchers used multiple regression to predict emotional distress as a function of the following independent variables. Identify each independent variable as quantitative or qualitative. For qualitative variables, suggest several levels that might be observed. For quantitative variables, give a range of values (levels) for which the variable might be observed.