Advertisements for skin care products often contain a phrase such as: “This product is clinically proven to. . . .” That statement may convince you to purchase a topical cream that claims to reduce acne, eliminate rough patches of skin, or lighten dark spots. You would be making this decision based on your belief in the following statement: If a product is clinically proven to do what it advertises, that means it will work for you.

Questions

1. “Clinically” generally implies that the product was subject to an experiment of some type. Describe the ideal type of experiment that would test whether a cream reduces acne.
2. Imagine that the results of this experiment showed that that there was a statistically significant difference in the extent of acne between those patients using the “real” cream and those using the placebo. Is this difference in acne necessarily large?
3. Much of the time, a “clinically proven” claim relies on consumer evaluation of the product—in other words,
surveys that ask whether acne was reduced as a result of using the product. What is the problem with this type of experimental approach?
4. Even if the experiment is well controlled and doubleblinded,
does the result of a single experiment prove a hypothesis?
5. Does this statistically significant result mean that everyone in the experiment who used the real cream had less acne than those who used the placebo?
6. Consider your answers to questions 1–5 and explain why the statement bolded above sounds right,
but isn’t.