An alternative biweight estimator based on Tukey's is examined in which (1) test disturbances are not assumed to be the same for all subjects, (2) each response is utilized proportional to its value, and (3) the biweight and maximum likelihood estimate agree when no disturbances are present. Smaller mean-squared errors are shown. (Author/CM)

Methods by which structural models correct for the effects of attenuation due to measurement error are reviewed, and implications of such disattenuation for interpreting the results of structural equation models are considered. Recommendations are made for improving the practice of disattenuation, and caution is urged in drawing inferences based…

The consequences of underextracting factors and components within and between the methods of maximum likelihood factor analysis and principal components analysis were examined through computer simulation. The principal components score and the factor score estimate (T. W. Anderson and H. Rubin, 1956) tended to become different with…

A program designed to administer questionnaires on IBM and IBM-compatible personal computers is described. The program prompts subjects to indicate responses by clicking on a graphic line segment or entering a numeric value. The program enhances accuracy in estimating moderating effects by overcoming transcriptional errors and scale coarseness.…

The effects of the base referent or standard stimulus on scale values obtained in the magnitude estimation scaling of 34 frequency expressions were studied with 208 undergraduate students and 2 different referents ("sometimes" and "fairly many times"). Analysis indicates that the two referents yield statistically similar…

A simulation study explored the effect of population distribution on maximum likelihood estimation (MLE) and expected a posteriori (EAP) estimation in computerized adaptive testing based on the rating scale model of D. Andrich (1978). The choice between EAP and MLE for particular situations is discussed. (SLD)

Although Camp's tetrachoric correlation approximation (B. Camp, 1934) has been shown to yield excellent results over a fairly wide range, its derivation remains something of a mystery. This article shows how Camp might have arrived at his formula using a theoretical, rather than an empirical, approach. (Author/SLD)

A Monte Carlo study compared the accuracy of different estimates of the standard error of correlations corrected for restriction in range. The procedure suggested by P. Bobko and A. Rieck (1980) generated the most accurate estimates of the standard error. Aspects of accuracy are discussed. (SLD)

Results from two Monte Carlo studies in item response theory (comparisons of computer item analysis programs and Bayes estimation procedures) are analyzed with inferential methods to illustrate the procedures' strengths. It is recommended that researchers in item response theory use both descriptive and inferential methods to analyze Monte Carlo…

A methodology for determining the optimal number of observations to use in a measurement design when resource constraints are imposed is presented. Two- and three-facet designs are outlined. Parallel closed form formulae can easily be determined for other designs. (TJH)

A method for estimating the first eigenvalue of random data correlation matrices is reported, and its precision is demonstrated via comparison to the method of S. J. Allen and R. Hubbard (1986). Data generated in Monte Carlo simulations with 10 sample sizes reaching up to 1,000 were used. (SLD)

Three correlation matrices (PEARSON, POLYCHORIC, and TOBIT) were used to obtain reliability estimates on ordered polytomous variable models. A Monte Carlo study with different levels of variable asymmetry and 400 sample correlation matrices demonstrated that the PEARSON matrix did not perform as well as did the other 2 matrices. (SLD)

Two alternatives to traditional item analysis and reliability estimation procedures are considered for determining the difficulty, discrimination, and reliability of optional items on essay and other tests. A computer program to compute these measures is described, and illustrations are given. (SLD)

A polychotomous nominal response model-based computerized adaptive test (CAT) was simulated using data from 1,093 University of Texas students. The ability estimation of this model and its overall performance were compared with those of a dichotomous three-parameter logistic model-based CAT. Advantages and drawbacks of nominal response CAT are…

Statistical significance and "abnormality" have been used as criteria for the evaluation of intra-individual subtest score differences. Shortcomings of these criteria are identified, and improved estimates of the true score differences are suggested. The applicability of the abnormality criterion to these improved estimates is reviewed.…