The crucial parts of the questionnaire were situations three and four. In situation three, subjects were provided with frequency information that would allow them to calculate the relative strength of the sexual behaviors as evidence of abuse. In situation four, subjects were provided with both base-rate and frequency information that would allow estimation of the probability of abuse in a particular child. When asked to prioritize the 12 cases as "high," "medium," or "low" on the basis of sexual behaviors, professionals were more accurate than students; however, when asked to estimate the probability of abuse in the single case, both professionals and students failed to incorporate base-rate information into their decisions. Consequently, both groups did not correctly estimate the probability of abuse under some circumstances. Professionals' performance on both judgment tasks was unrelated to level of experience with sexual abuse cases. 2 tables, 19 references, and appended example of questionnaires used in study