There are currently three main approaches to parameter estimation in item response theory (IRT): (1) joint maximum likelihood, exemplified by LOGIST, yielding maximum likelihood estimates; (2) marginal maximum likelihood, exemplified by BILOG, yielding maximum likelihood estimates of item parameters (ability parameters can be estimated…

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 method for estimating power scores is described. By way of illustration, it is applied to 21 students who were improperly timed on a standard test. Some empirical results are given in support of the estimation procedure. (Author)

A general Computer program is described that will compute asymptotic standard errors and carry out significance tests for an endless variety of (standard and) nonstandard large-sample statistical problems, without requiring the statistician to derive asymptotic standard error formulas. The program assumes that the observations have a multinormal…

An elementary survey of item characteristic curve theory, centered around the problems of individualized (tailored) testing, is presented. Following the introduction, discussions are provided of the following: Test Theory for Itemized Tests; The Guttman Scale; Item Characteristic Curve Theory; An Alternative Model; Specialization, Application, and…