Abstract: A method of measuring the effectiveness of a surgical or medical treatment carried out on a patient population is provided. The method involves the steps of selecting a patient population, deriving pre-treatment score and post-treatment scores for each patient based on their questionnaire responses to quality of life-related criteria, deriving an adjusted score by subtracting the pre-treatment score from the post-treatment score, and analyzing the distribution of patients having each adjusted score to provide a measure of the effectiveness of the surgical or medical treatment. The population of patients may includes patients having different values of a variable affecting the effectiveness of the surgical treatment. The effect of these variables on the adjusted scores may be analyzed by a computerized statistical software program.