The researchers are trying to avoid confounding. Socioeconomic status might be a lurking variable.
Work Step by Step
Maybe adolescents of a higher socioeconomic status eat more and, then, have higher body mass index.
You can help us out by revising, improving and updating this answer.Update this answer
After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.