An article entitled Couch potato nation describes a report by the federal Centers for Disease Control and Prevention that "analyzed responses from 119,000 people who were asked in 1996 about their physical activity during the month prior to the survey."20
a. This was an observational study. Was it retrospective or prospective?
b. The article states that overall, nearly 30% of adults reported being inactive. Is physical activity treated here as a quantitative or a categorical variable?
c. It was also reported that the rate of inactivity was 37% in small towns, compared with a rate of 27% in large urban areas. Now there are two variables of interest; describe the explanatory variable and tell whether it is quantitative or categorical.