Presently available test statistics for the Rasch model are shown to be insensitive to violations of the assumption of test unidimensionality. Two new statistics are presented. One is similar to available statistics, but with some improvements; the other addresses the problem of insensitivity to unidimensionality. (Author/JKS)

For the six available sets of empirical data, the discrimination (slope) parameter of the logistic item characteristic curve was found to have a significant positive correlation over items with the difficulty (location) parameter. This unpleasant situation can be eliminated by a suitably chosen transformation of the ability scale. (Author/RC)

Social and naturally occurring choice phenomena are often of the "pick any" type in which the number of choices made by a subject as well as the set of alternatives from which they are chosen is unconstrained. A model and scaling method for these data are introduced. (Author/JKS)

Omitted items cannot properly be treated as wrong when estimating ability and item parameters. A convenient method for utilizing the information provided by omissions is presented. Theoretical and empirical justifications are presented for the estimates obtained by the new method. (Author)