A social research methods class wants to study smoking. First, the professor asks how many people in the class are smokers. Two people indicate that they are. Then she asks how many people have smoked a cigarette in the past week and ten people indicate that they had. From this, the class decides, for the purposes of the survey, a smoker will be anyone who has smoked a cigarette in the past week and currently owns a pack of cigarettes. This is a(n):.
a. ethical challenge.
b. ethnography.
c. hypothesis.
d. operational definition.
e. spurious correlation.