Comparison of Three Procedures for Smoothing Score Distributions

Distributions of test scores need to be smoothed in equating and/or norming. Popular parametric smoothing procedures are based on beta-binomial and log-linear models. A new approach has been developed using polynomials of the beta-binomial cumulative distribution function. The same approach was also applied to extend the beta-binomial family to more than four parameters. These methods were compared using cross-validation in two examinee samples who took the Armed Services Vocational Aptitude Battery. Results show that the log-linear and extended beta-binomial families fit the data about equally well.