The test is whether the believers are expert. [fact]
The popular acceptance of a policy or practice does not show it to be wise; the fact that a great many people hold to a given opinion does not prove it to be true. The test is whether the believers are expert or at least competent in the field, or on the particular proposition believed.
Ruggero J. Aldisert, Agatha D. Aldisert, Logic for Lawyers- A Guide …, loc. 1061