For six tests, coefficient delta as an index for internal optimality is computed. Internal optimality is defined as the magnitude of risk of the decision procedure with respect to the true score. Results are compared with an alternative index (coefficient kappa) for assessing the consistency of decisions. (Author/JKS)

Abuses and misuses of statistics are frequent. This digest attempts to warn against these in three broad classes of pitfalls: sources of bias, errors of methodology, and misinterpretation of results. Sources of bias are conditions or circumstances that affect the external validity of statistical results. In order for a researcher to make…

In a multiple (or multivariate) regression model where the predictors are subject to errors of measurement with a known variance-covariance structure, two-sample hypotheses are formulated for (i) equality of regressions on true scores and (ii) equality of residual variance (or covariance matrices) after regression on true scores. The hypotheses…

Some of the issues faced by institutions as they attempt to design a system of constructs that reflects the diversity of their schools are addressed. The choice of statistic, percentage passing versus mean, used in reporting test results can impact the allocation of services to subpopulations in the school. Percent passing statistics tend to focus…