The authors discuss the applicability of nonparametric item response theory (IRT) models to the construction and psychometric analysis of personality and psychopathology scales, and they contrast these models with parametric IRT models. They describe the fit of nonparametric IRT to the Depression content scale of the Minnesota Multiphasic Personality Inventory--2 (J. N. Butcher, W. G. Dahlstrom...

The progress test is used to provide useful summative and formative judgments about medical students' knowledge without distorting learning. The test samples the complete knowledge domain expected of new graduates on completion of their course, regardless of the year level of the student. Item Response Theory (IRT) have been proposed for evaluating examinations in medical education. Although IR...

We compare test construction using CTT and IRT in several sample sizes (from N=20 to N=5000) and degrees of representativeness (represented by selecting the top 20%, 40%, 60%, 80% or 100% of a population) using a Monte-Carlo simulation design. Little support was found for our hypothesis that IRT would outperform CTT in building informative tests, especially in large or unrepresentative samples....

Immunoreactive trypsin (IRT) content in blood spots from 17 cystic fibrosis (CF) children born between 1975-80 were assayed with reagents from two commercial radioimmunoassay kits. The manufacturers' procedures were modified to allow assay of blood spot IRT. Half of the CF samples had a significantly raised IRT content compared to normal blood spots. Of the blood spots from five children whose ...

This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-worl...

Anaemia is common in advanced cancer, may develop for several reasons, and is not always symptomatic. Our observations of the seemingly indiscriminate prescription of iron-replacement therapy (IRT) for anaemic palliative care patients, and our practice of discontinuing IRT in patients with normal red-cell indices, prompted a study to determine (1) the prevalence of anaemia in our patients, (2) ...

BACKGROUND The Washington Radiation for In-Stent Restenosis Trial is a double-blinded randomized study evaluating the effects of intracoronary radiation therapy (IRT) in patients with in-stent restenosis (ISR). METHODS AND RESULTS One hundred thirty patients with ISR (100 native coronary and 30 vein grafts) underwent percutaneous transluminal coronary angioplasty, laser ablation, rotational a...

OBJECTIVE To investigate variation in immunoreactive trypsinogen (IRT) concentrations by race, sex, birth weight, and gestational age and their implications for the use of percentile-based cutoffs for cystic fibrosis (CF) newborn screening (NBS) programs. PATIENTS AND METHODS This cross-sectional population-based study of resident infants screened in Michigan investigates associations between...