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)

A number of empirical studies are suggested to answer certain questions in connection with flexilevel tests. (MS)

A common problem arises in scale transformation when independent estimates of item parameters from two separate data sets must be expressed in the same metric. These item parameter estimates will be different because the metric or scale defined by each independent calibration of the items is different. The problem is frequently confronted in…

The purpose of this book is to make it possible for measurement specialists to solve practical testing problems through the use of item response theory (IRT). The topics, organization, and presentation are those used in a 4-week seminar held each summer for the past several years. The material is organized to facilitate understanding; all related…

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)