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%A Siu L. Chow %J Psychological Bulletin %T Significance Test or Effect Size? %X I describe and question the argument that in psychological research, the significance test should be replaced (or, at least, supplemented) by a more informative index (viz., effect size or statistical power) in the case of theory-corroboration experimentation because it has been made on the basis of some debatable assumptions about the rationale of scientific investigation. The rationale of theory-corroboration experimentation requires nothing more than a binary decision about the relation between two variables. This binary decision supplies the minor premise for the syllogism implicated when a theory is being tested. Some metatheoretical considerations reveal that the magnitude of the effect-size estimate is not a satisfactory alternative to the significance test. %N 1 %K statistical significance, effect size, statistical power, meta-analysis, modus tollens, the sample-size problem, theeffect-size problem, the substantive-significance problem, theory corroboration %P 105-110 %V 103 %D 1988 %L cogprints824