4. The method of claim 1 wherein the cohort analysis mechanism determines an answer to the question using evidence gathered from a set of cohorts where case attributes in the set of cohorts does not match exactly attributes of the person in the question.
4. The method of claim 1 wherein the cohort analysis mechanism determines an answer to the question using evidence gathered from a set of cohorts where case attributes in the set of cohorts does not match exactly attributes of the person in the question. 5. The method of claim 4 wherein the question is a medical question for a patient and the cohort analysis mechanism processes the medical history of the patient and finds the cohorts from medical histories of other patients to predict an answer from the cohorts.