Advances in Physiology Education, Vol 267, Issue 6 113-S119, Copyright © 1994 by American Physiological Society
Certainty and uncertainty in science: the subjectivistic concept of probability in physiology and medicine
R. Jevning, R. Anand and M. Biedebach
Department of Biological Sciences, California State University, Long Beach 90840.
Most physiological scientists have restricted understanding of probability
as relative frequency in a large collection (for example, of atoms). Most
appropriate for the relatively circumscribed problems of the physical
sciences, this understanding of probability as a physical property has
conveyed the widespread impression that the "proper" statistical "method"
can eliminate uncertainty by determining the "correct" frequency or
frequency distribution. However, many relatively recent developments in the
theory of probability and decision making deny such exalted statistical
ability. Proponents of Bayes's subjectivist theory, for example, assert
that probability is "degree of belief," a more tentative idea than relative
frequency or physical probability, even though degree of belief assessment
may utilize frequency information. In the subjectivist view, probability
and statistics are means of expressing a consistent opinion (a probability)
to handle uncertainty but never means to eliminate it. In the physiological
sciences the contrast between the two views is critical, because problems
dealt with are generally more complex than those of physics, requiring
judgments and decisions. We illustrate this in testing the efficacy of
penicillin by showing how the physical probability method of "hypothesis
testing" may contribute to the erroneous idea that science consists of
"verified truths" or "conclusive evidence" and how this impression is
avoided in subjectivist probability analysis.
