Orthopaedic surgeons have recognized for a long time the importance of end-result studies, and the analyses of such reports abound in orthopaedic journals. Most studies were designed to answer definite questions relative to the results of a specific operation. To this purpose, the authors of reports on end-result studies of cup arthroplasty of the hip, for example, collected data on range of motion, degree of limp, residual pain, complications, duration of operation, time of hospitalization, etc. This data was sorted into categories of diagnoses, age groups, length of follow-up, sex or as many other categories as necessary to provide categorical information.