To rule out the need for a two-parameter item response theory (IRT) model during item analysis by Rasch models, it is important to check the Rasch model's assumption that all items have the same item discrimination. Biserial and polyserial correlation coefficients measuring the association between items and restscores are often used in an informal…

The norm-referenced score scale used by the National Foundation for Educational Research (NFER) is described. The usefulness of standardized scores is explained by a simple numerical example, and the formulas and computations are shown for calculating a mean, a standard deviation, and a deviation or z score. The need for a representative sample is…