The focus of this paper is assessing the impact of measurement errors on the prediction error of an observed-score regression. Measures are presented and described for decomposing the linear regression's prediction error variance into parts attributable to the true score variance and the error variances of the dependent variable and the predictor…

The assessment of positive affect (PA) and negative affect (NA) by means of the Positive Affect and Negative Affect Schedule has received a remarkable popularity in the social sciences. Using a meta-analytic tool--namely, reliability generalization (RG)--population reliability scores of both scales have been investigated on the basis of a random…

Longitudinal studies are permeating clinical trials in psychiatry. Therefore, it is of utmost importance to study the psychometric properties of rating scales, frequently used in these trials, within a longitudinal framework. However, intrasubject serial correlation and memory effects are problematic issues often encountered in longitudinal data.…

Background: A recent article published in "Educational Research" on the reliability of results in National Curriculum testing in England (Newton, "The reliability of results from national curriculum testing in England," "Educational Research" 51, no. 2: 181-212, 2009) suggested that: (1) classification accuracy can be…

It is shown that the Angoff and bookmarking cut scores are examples of true score equating that in the real world must be applied to observed scores. In the context of defining minimal competency, the percentage "failed" by such methods is a function of the length of the measuring instrument. It is argued that this length is largely…

Physician-patient communication is a clinical skill that can be learned and has a positive impact on patient satisfaction and health outcomes. A concerted effort at all medical schools is now directed at teaching and evaluating this core skill. Student communication skills are often assessed by an Objective Structure Clinical Examination (OSCE).…

Proposes true score models that can account for correlated errors and their effect on coefficient alpha. These models allow random measurement errors on earlier items to affect directly or indirectly the scores on later items. Conditions under which coefficient alpha may yield spuriously high estimates or reliability are discussed. (SLD)

This study evaluated the impact of unequal reliability on test equating methods in the nonequivalent groups with anchor test (NEAT) design. Classical true score-based models were compared in terms of their assumptions about how reliability impacts test scores. These models were related to treatment of population ability differences by different…

The paradox that a Student t-test based on pretest-posttest differences can attain its greatest power when the difference score reliability is zero was explained by demonstrating that power is not a mathematical function of reliability unless either true score variance or error score variance is constant. (SLD)

Examined the stability of the standard error of measurement and the relationship between the reliability coefficient and the variance of both true scores and error scores for 170 school districts in a state. As expected, reliability coefficients varied as a function of group variability, but the variation in split-half coefficients from school to…

Numerous studies have shown increasing item reliabilities as an effect of the item position in personality scales. Traditionally, these context effects are analyzed based on item-total correlations. This approach neglects that trends in item reliabilities can be caused either by an increase in true score variance or by a decrease in error…

The standard error of measurement as a means for estimating the margin of error that should be allowed for in test scores is discussed. The true score measures the performance that is characteristic of the person tested; the variations, plus and minus, around the true score describe a characteristic of the test. When the standard deviation is used…

The distinction between two models of reliability is clarified. Reliability may be conceived of and estimated from a true score model or from the perspective of sampling precision. Basic models are developed and illustrated for each approach using data from the author's work on measuring organizational climate. (SLD)

Supposing different values of the standard measurement error, the relation of scale coarseness to the total amount of error is studied on the basis of probability distribution of error. The analyses are performed within two models of error and with two criteria of amount of error. (Editor/SJL)

A distinction is made between reliability of measurement and reliability of classification; the "criterion-referenced reliability coefficient" describes the former. Application of this coefficient to the probability distribution of possible scores for a single student yields a meaningful way to describe the reliability of a single score. (Author)