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 parsley with the same instructions and same diet. A nurse at the nutrition center weighs each subject on Friday of each week. Select the potential source of confounding.
A. Placebo effect
B. Experimenter effect
C. Method of assignment to treatment and control groups
D. The study is essentially free of potential confounding.
Answer: A
Agree.
To determine the potential source of confounding in this study, we need to understand the different factors that could influence the results and introduce bias. In this scenario, the potential sources of confounding are:
A. Placebo effect: This refers to the psychological impact experienced by the participants due to their belief in receiving a treatment, even if it is a placebo. Since both groups receive a substance (herb or parsley) with instructions, there is a possibility that the placebo effect could confound the results by influencing the participants' perceptions and behaviors.
B. Experimenter effect: This refers to the potential bias that can emerge from the behavior or actions of the nutritionist conducting the study. If the nutritionist inadvertently treats the two groups differently or influences them in any way (e.g., through unintentional cues or communication), it could lead to biased results.
C. Method of assignment to treatment and control groups: This factor is related to how participants are randomly assigned to either the treatment or control group. If the random assignment process is not properly conducted or if there is potential for bias in how participants are chosen, it could introduce confounding variables.
D. The study is essentially free of potential confounding: This answer choice suggests that there is no potential source of confounding in the study, which is unlikely in most research studies. Randomized controlled trials like this one can still have potential confounding factors, which need to be carefully accounted for in order to minimize bias.
In this case, the potential source of confounding is most likely A. Placebo effect, as the participants' beliefs and expectations about receiving a treatment (herb or parsley) could influence their weight loss outcomes. It is important for the nutritionist to understand and address this potential bias when interpreting the study's results.