Comparisons are made between BILOG version 2.2 and LOGIST 5.0 version 2.5 in estimating the item parameters, traits, item characteristic functions, and test characteristic functions for the three-parameter logistic model. Speed and accuracy are reported for a number of 10, 20, and 40-item tests. (Author/GDC)

This paper develops and applies three nonparametric comparisons of the shapes of two item characteristic surfaces: (1) proportional latent odds; (2) uniform relative difficulty; and (3) item sensitivity. A method is presented for comparing the relative shapes of two item characteristic curves in two examinee populations who were administered an…

A method is presented for estimating the item characteristic curve (ICC) using polynomial regression splines. Estimation of spline ICCs is described by maximizing the marginal likelihood formed by integrating ability over a beta prior distribution. Simulation results compare this approach with the joint estimation of ability and item parameters.…