An economist conducted a study of the possible association between weekly income and weekly grocery expenditures. Of particular interest was whether higher income would result in shoppers to spending more on groceries. A random sample of shoppers at a local supermarket was obtained. A questionnaire was administered asking about the weekly income of each Shopper's family and their grocery bill for that week. The explanatory variable is: 0 gender. 0 All of the answer options are correct. 0 weekly expenditure. 0 weekly income