Three methods of test equating (linear, equipercentile, and item response theory) were investigated with respect to the issue of scale drift. Results indicate that all three models work well in limited settings but that the item response theory approach provided the most stable results overall. (JKS)

Type I error rates for Yao's, James' first-order and second-order, and Johansen's tests of equality of mean vectors for two independent samples were estimated for various conditions defined by the degree of heteroscedasticity and nonnormality. Each procedure can be seriously nonrobust with exponential and log-normal distributions. (TJH)