Question

Side effects Even if an experiment is double-blind, the blinding might be compromised if side effects of the treatments differ. For example, suppose researchers at a skin-care company are comparing their new acne treatment against that of the leading competitor. Fifty subjects are assigned at random to each treatment, and the company’s researchers will rate the improvement for each of the $100$subjects. The researchers aren’t told which subjects received which treatments, but they know that their new acne treatment causes a slight reddening of the skin. How might this knowledge compromise the blinding? Explain why this is an important consideration in the experiment.

Short answer

The lack of blinding may bias the reported results because the results may be influenced by the placebo effect.

Step-by-step solution

Given information

We need to find how might this knowledge compromise the blinding and why this is an important consideration in the experiment.

Simplify

In a double-blind experiment, neither the subjects nor the people who measure them know which treatment they had, whereas in a single-blind experiment, either the people who measure or the people who get the results know which treatment they got (but not both).
The personnel who measure the treatment results will understand which treatment the participants received (due to skin reddening or not), and it may impact how they measure the results since they want the new drug to work, thus they may (perhaps subconsciously) modify the data considerably.