title: Optimal discrimination index and discrimination efficiency for essay questions.
abstract: Recommended guidelines for discrimination index of multiple choice questions are often indiscriminately applied to essay type questions also. Optimal discrimination index under normality condition for essay question is independently derived. Satisfactory region for discrimination index of essay questions with passing mark at 50% of the total is between 0.12 and 0.31 instead of 0.40 or more in the case for multiple-choice questions. Optimal discrimination index for essay question is shown to increase proportional to the range of scores. Discrimination efficiency as the ratio of the observed discrimination index over the optimal discrimination index is defined. Recommended guidelines for discrimination index of essay questions are provided.
authors: Office of Educational Services, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, chan50b@gmail.com.
authors: Wing-shing
authors: WS
authors: Chan
mesh_terms: D000124:Achievement; D016002:Discriminant Analysis; D004521:Educational Measurement / Q000706:statistics & numerical data*; D019983:Guideline Adherence; D006801:Humans; D015233:Models, Statistical; D011594:Psychometrics / Q000706:statistics & numerical data*; D016008:Statistical Distributions; D014956:Writing