Discussion of probabilistic information retrieval systems highlights the probability ranking principle and discusses when the standard retrieval policy is optimal. Topics discussed include calibration and refinement; independent assessment of relevance by the inquirer; certainty about the computed probabilities of relevance; and confidence and…

Cohen's (TM 504 890) formal rules of intuitive probability lack normative or descriptive appeal, and his interpretation of the author's findings is not compelling. (CP)

Until recently, norms of experimental reasoning have lacked systematic theoretical development. Thus, it has been easy for psychologists like Tversky and Kahneman to misclassify certain human reasoning processes as being Pascalian and invalid, rather than as being Baconian and valid. (CP)