A nutritionist wants to conduct a study to validate the efficacy of an herb as an aid in weight loss. She randomly assigns half of a group of overweight persons to a treatment group who are given the herb with instructions for its use and a planned diet for six weeks. The other half of the group is given the same diet without the herb. A nurse at the nutrition center weighs each subject on Friday of each week. Select the potential source of confounding.
A) The placebo effect
B) Method of assignment to treatment and control groups
C) Experimenter effect
D) The study is essentially free of confounding sources.

Question

Quizplus · Accepted Answer

The placebo effect can be a source of confounding because participants in the control group might experience weight loss simply because they believe they are being treated, even though they are not receiving the herb.

A Nutritionist Wants to Conduct a Study to Validate the Efficacy