AN ANALYTICAL PROCEDURE FOR THE EQUIPERCENTILE METHOD OF EQUATING TESTS

Prior use of the equipercentile method of test equating was based on a graphic procedure which is tedious, subject to smoothing errors, and nonanalytical. Recognition of the equipercentile method as a curve-fitting procedure for two cumulative percentage distributions leads to a proposed analytical solution to the problem through use of linear estimates for successive "missing" cumulative percentage points. A complete equipercentile procedure which uses the proposed method and provides linear and quadratic functions for goodness-of-fit and extrapolation is discussed and illustrated with data from a test equating project.