ABSTRACT
Chapter 5 of ARM 4th Ed is entitled Invariance: A Crucial Property of Scientific Measurement. Measurements of differences, including change over time, require data collection instruments whose calibrations remain stable over time and across samples of interest. The stability of item and person measures is termed measurement invariance: “You can’t measure change with a measure that changes.” Rasch measurement procedures for examining invariance for items, persons and subgroups, as well as constructing vertical scales with Rasch analysis are introduced and explained. Differential Item Functioning (DIF) is illustrated as a failure of measurement invariance. Step-by step instructions for techniques used to examine invariance are provided on the book website.
