The variable employment status is not a possible confounder in this study. Choose the best reason why. 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, all of the participants in the sample had full-time employment status. So, each person in the sample could participate since they could be placed into one of the two groups. 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 yearly income, and the treatments are needing corrective lenses and not needing corrective lenses.) In this study, both treatment groups (corrective lenses and no corrective lenses) were similarly comprised of only participants who were employed full-time. Thus, the researcher designed the study so that a participant's employment status would not be a confounder