  The customary use of P-values in scientific research has been attacked as
being ill-conceived, and the utility of P-values has been derided. This paper
reviews common misconceptions about P-values and their alleged deficits as
indices of experimental evidence and, using an empirical exploration of the
properties of P-values, documents the intimate relationship between P-values
and likelihood functions. It is shown that P-values quantify experimental
evidence not by their numerical value, but through the likelihood functions
that they index. Many arguments against the utility of P-values are refuted and
the conclusion is drawn that P-values are useful indices of experimental
evidence. The widespread use of P-values in scientific research is well
justified by the actual properties of P-values, but those properties need to be
more widely understood.

Methodology