Question

(d) suppose the researcher is interested in reducing the effect that differences in income might have on average monthly grocery bills between the vegetarian and meat - eating groups. what is a reasonable approach for the researcher to take? choose the best answer from the choices below. the researcher could divide the adults in the vegetarian group into two groups: those with annual income over $50,000 and those with annual income under $50,000. she would divide the meat - eating participants into two groups as well, based on education level: graduated from high school and did not graduate from high school. then the average monthly grocery bill could be compared between the vegetarians whose annual income is under $50,000 and meat - eaters who graduated high school. the researcher could aim to select a vegetarian and then find a meat - eater who has a similar annual income as the vegetarian. she could continue to create pairs of participants in this way, such that each pair of vegetarian and meat - eating participants have similar annual incomes. this would result in two groups of participants, each comprised of people with a similar mix of annual incomes. then the researcher could compare the average monthly grocery bill between the vegetarian and meat - eating groups. the researcher could increase the sample size. increasing the sample size helps to reduce the effect that confounding variables have on the outcome of the study. a sample size of at least 1000 participants is recommended to control for unwanted variation in a study.

Explanation:

The goal is to control for the confounding variable (income) to isolate the relationship between diet (vegetarian/meat-eating) and monthly grocery bills. The best approach is to create matched groups where income (the key confounding factor) is similar between vegetarians and meat-eaters, so any difference in grocery bills can be more reliably attributed to diet. Increasing sample size does not directly control for income, and splitting groups by income and education adds an extra variable that is not the target confounder here.

Answer:

○ The researcher could aim to select a vegetarian and then find a meat-eater who has a similar annual income as the vegetarian. She could continue to create pairs of participants in this way, such that each pair of vegetarian and meat-eating participants have similar annual incomes. Then the researcher could compare the average monthly grocery bill between the vegetarian and meat-eating groups.