The cold cleared up after the supplement. Proof?

Question

A wellness company gives a new herbal supplement to 200 people who currently have a cold. Within a week, almost all of them report feeling much better, and the company markets the supplement as a proven cold cure.

Why does this evidence not show the supplement works, and what is missing?

Accepted Answer

Colds get better on their own. Most common colds clear up within about a week no matter what you do. So "almost everyone recovered within a week" is precisely the outcome you would see if the supplement did absolutely nothing. The company measured recovery in the treated group but never measured recovery in an untreated group over the same week. Why people started treatment matters too. People tend to reach for a remedy when they feel worst. From a low point, the natural next move is up regardless of treatment, a pattern called regression to the mean. That alone can make any remedy look effec…

The cold cleared up after the supplement. Proof?

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