Validation of questionnaires on physical function

Data-gathering instruments were used in a randomized controlled trial, designed to assess a structured preoperative educational program for elective surgical patients. The key dependent variable was the physical functional capacity of patients following surgery. Questionnaires were developed to measure physical functioning in the immediate postoperative period, after discharge from hospital, and 10 days and 33 days after surgery. Statistical techniques used to measure interobserver agreement and bias were worker's chi square, Cicchett's statistic, the contingency coefficient, Kendall's Taub, and Kendall's coefficient of concordance W. The standardized questionnaires permitted classification of patients's postoperative physical functions with results that agreed highly with the classification done by experienced clinicians who cared for the same patients.