The variable marital status is not a possible confounder in this study. Choose the best reason why. A variable is a confounder if its effect on the outcome cannot be distinguished from the effect on the outcome from different treatments. (In our context, the outcome is the monthly grocery bill, and the treatments are being a vegetarian and being a meat-eater.) In this study, both treatment groups (vegetarian and meat-eater) were similarly comprised of only participants who were single (unmarried). Thus, the researcher designed the study so that a participant's marital status would not be a confounder. A variable is a confounder if, based on its value, it prohibits some members of the sample from participating in the study. For this study, there were no adults in the sample who were not married. So, each adult in the sample could participate since they could be placed into one of the two groups