Optimum examinee samples for item parameter estimation in item response theory: A multi-objective programming approach

This paper proposes a multi-objective programming method for determining samples of examinees needed for estimating the parameters of a group of items. In the numerical experiments, optimum samples are compared to uniformly and normally distributed samples. The results show that the samples usually recommended in the literature are well suited for estimating the difficulty parameters. Furthermore, they are also adequate for estimating the discrimination parameters in the three-parameter model, butnot for the guessing parameters.     

Specifying optimum examinees for item parameter estimation in item response theory

Information functions are used to find the optimum ability levels and maximum contributions to information for estimating item parameters in three commonly used logistic item response models. For the three and two parameter logistic models, examinees who contribute maximally to the estimation of item difficulty contribute little to the estimation of item discrimination. This suggests that in applications that depend heavily upon the veracity of individual item parameter estimates (e.g. adaptive testing or text construction), better item calibration results may be obtained (for fixed sample sizes) from examinee calibration samples in which ability is widely dispersed.This work was supported by Contract No. N00014-83-C-0457, project designation NR 150-520, from Cognitive Science Program, Cognitive and Neural Sciences Division, Office of Naval Research and Educational Testing Service through the Program Research Planning Council. Reproduction in whole or in part is permitted for any purpose of the United States Government. The author wishes to acknowledge the invaluable assistance of Maxine B. Kingston in carrying out this study, and to thank Charles Lewis for his many insightful comments on earlier drafts of this paper.     

Two field studies on the effects of alcohol on eyewitness identification,confidence, and decision times

In two field studies, bar tenants (Ns = 86 and 190, respectively) were successively approached by confederates C1 and C2 on a night out. Confederate C3 then presented participants with a six‐person target‐absent or target‐present lineup concerning C1 or C2 (immediate test). Several days later, participants viewed a lineup regarding the confederate they had not attempted to identify earlier (C1/C2; delayed test). An immediate compared with a delayed, sober identification test did not increase the risk of a false identification decision. A blood alcohol concentration of 0.06–0.07% best discriminated accurate from inaccurate decisions. Choosers with a blood alcohol concentration ≤ 0.06% showed excellent calibration and little overconfidence, and their confidence was a strong indicator of accuracy (i.e., good resolution). Choosers with a higher intoxication level displayed poor calibration and strong overconfidence. Nonchoosers were generally poorly calibrated. Combined analyses showed a negative effect of intoxication on one's ability to discriminate the target from nontargets.     

The Case of the Vanishing Optimum

It is not only people who may disappear, nor one's keys. It may also be the optimum that one was so certain of being able to grasp and that so suddenly reveals itself to be totally elusive. And the situation then becomes dramatic, as with people, or utterly confused, as with the loss of keys: a familiar element is suddenly missing and one does not know how, nor where, to look for it. However, in contrast with the disappearance of a person that provokes action based on rational behaviour—notification of the police, broadcasting of a notice of search—the disappearance of the optimum begets reactions that are unpredictable, irrational or even ideological. Instead of its absence being accepted and action taken accordingly, its absence is denied. Why does the optimum vanish under certain conditions? And why does one not accept to admit that fact? Those are the two questions that we shall examine. We shall start with the second one, which presents a more straightforward approach to the problem.