For detecting differential item functioning (DIF) between two or more groups of test takers in the Rasch model, their parameters need to be placed on same scale. Typically this is done by means choosing a set so-called anchor items based statistical tests heuristics. Here authors suggest an alternative strategy: By inequality criterion from economics, Gini Index, are shifted optimal position wh...

Linear mixed-effects models are widely used in applications to analyze clustered, hierarchical, and longitudinal data. Model selection linear mixed is more challenging than that of as the parameter vector a model includes both fixed effects variance component parameters. When selecting components random effects, must be non-negative parameters may lie on boundary space. Therefore, classical met...