Imagine we wanted to investigate whether a person's profession can predict scores on a self-report psychopathy scale. We collected data from people in eight different professions and a group of unemployed people. The eight professions were: bank traders, insurance brokers, health care professionals, business executives, volunteer workers, full-time mums, teachers, construction workers. The outcome was psychopathy score. If we wanted to analyse these data using regression, how many dummy variables would we need?
A)7
B)It is not possible to analyse these data with regression.
C)8
D)9

Question

Quizplus · Accepted Answer

Since there are eight different professions, we need to create dummy variables for each of them. The unemployed group is the reference group, so we do not need a dummy variable for them. Therefore, we need eight dummy variables, which gives us a total of nine variables (including the intercept).

Imagine We Wanted to Investigate Whether a Person's Profession Can