Everyone knows it is easy to lie with statistics. It is important then
to be able to tell a statistical lie from a valid statistical inference.
It is a relatively widely accepted commonplace that our scientific
knowledge is not certain and incorrigible, but merely probable, subject
to refinement, modifi- cation, and even overthrow. The rankest beginner
at a gambling table understands that his decisions must be based on
mathematical ex- pectations - that is, on utilities weighted by
probabilities. It is widely held that the same principles apply almost
all the time in the game of life. If we turn to philosophers, or to
mathematical statisticians, or to probability theorists for criteria of
validity in statistical inference, for the general principles that
distinguish well grounded from ill grounded generalizations and laws, or
for the interpretation of that probability we must, like the gambler,
take as our guide in life, we find disagreement, confusion, and
frustration. We might be prepared to find disagreements on a
philosophical and theoretical level (although we do not find them in the
case of deductive logic) but we do not expect, and we may be surprised
to find, that these theoretical disagreements lead to differences in the
conclusions that are regarded as 'acceptable' in the practice of science
and public affairs, and in the conduct of business.