Significance tests and the duplicity of binary decisions.

Presents a logical justification for the following statements and discusses their implications: It is duplicitous (misleading) to use significance tests for making binary (either/or) decisions regarding the validity of a theory; the binary choice between calling results significant or not significant should not govern the confidence placed i n a theory, because such confidence cannot be gained in the either/ or fashion characterizing deductive certainty. The implications include grounds for describing ways that effect size estimates become useful in makingjudgments about the value of theories. Charles Sanders Peirce, who some say was Americas greatest philosopher of science, wrote that science can only rest on experience; he then added that experience can never result in absolute certainty, exactitude, or universality (Buchler, 1955, p. 47). Hypothesis-testing procedures make explicit sciences lack of certainty. In particular, inferential statistics provide estimates of whether a finding reflects merely random variation, an outcome owing to chance rather than to causal mechanisms hypothesized by theories. I contend that such procedures can