Ineffective therapies can appear to produce convincing improvements in diseases.

Question

Ineffective therapies can appear to produce convincing improvements in diseases. Piantadosi (Sec 6.6.1, optional course text in syllabus) claims that there are at least 3 mechanisms by which this happens: (1) spontaneous improvements in the disease, (2) regression to the mean, and (3) the placebo effect. Consider the following scenario: Patients with severe emphysema are enrolled into a blinded, randomized trial testing Drug A vs Placebo. The outcome of interest is a measure of exercise capacity known as the "Six-Minute Walk Test (6MWT)," in which the distance a patient can walk in 6 minutes on a flat surface is measured (in meters) The 6MWT is administered at baseline and 6 months after the start of study treatment. Now suppose that the placebo group had 6-month outcomes that were surprisingly better than at baseline. Describe how each of the 3 mechanisms might be contributing to this improvement.

Explanation / Answer

In an experiment, the placebo group had better outcome than the treatment group. This could be due to following reasons,

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