Bootstrap Equating Errors for the Common-item Nonequivalent Groups Design: A Comparison of Rasch Equating Methods

Abstract

The nonequivalent groups with anchor test (NEAT) equating design are traditionally based on using a single anchor to adjust for differences in test difficulty which is critical to equating test forms in most large-scale testing programs. When tests differ somewhat in content and length, methods based on the item response theory (IRT) model leads to greater stability of equating results. The current study compared standard errors, bias, and root mean square errors using four Rasch IRT equating methods for the nonequivalent groups with anchor test design. The sizes of the equating anchor were employed in all four different Rasch equating methods to investigate how different anchor sizes may impact the test accuracy of the tests by conducting a simulation study.