Monte Carlo estimation of the conditional Rasch model

In order to obtain conditional maximum likelihood estimates, the so-called conditioning estimates have to be calculated. In this paper a method is examined that does not calculate these constants exactly, but approximates them using Monte Carlo Markov Chains. As an example, the method is applied to the conditional estimation of both item and person parameters in the Rasch model. The key idea for this approach was developed by C. J. Geyer and E. A. Thompson (1992), who showed that, in the exponential family, a quantity that is proportional to the conditioning constant can be expressed as an expectation with respect to a certain distribution. Simulating from this distribution, an estimate of the proportional quantity can be obtained as the observed sample mean. Inserting this estimate into the conditional likelihood then allows one to maximize the approximate likelihood, as the proportionality constant does not depend on the parameters to be estimated

Studies on statistical models for polytomously scored test items

This dissertation, which is structured as a collection of self-contained papers, will be concerned mainly with di�erences between item response models. The purpose of item response theory (IRT) is estimation of a hypothesized latent variable, such as, for example, intelligence or ability in geography

Two-dimensional sociometric status determination with rating scales : a probability and a standard score method

This article addresses the interrelationship of employee rights to engage in concerted activities under Section 7 of the National Labor Relations Act (NLRA) and employer policies on electronic mail (e-mail) use. Should traditional labor law rules regarding solicitation and distribution be applied to e-mail communication? Does a business-use-only e-mail policy avoid legal problems? Is such a policy practical in light of the pervasive use of e-mail for general communication? If employers permit selective personal use of the e-mail system, but prohibit discussions related to a union, or to wages, hours and working conditions, such discrimination is legally problematic. Also, employer monitoring of employee e-mail is a form of surveillance that may be prohibited during a union organizational campaign. This article analyzes existing case law interpreting similar issues under the NLRA in light of new issues arising with e-mail in the workplace. The article concludes with recommendations for appropriate resolution of the competing interests of employers, unions, and employees