ABSTRACT
This chapter presents the methodology and procedures of testing for item and person fit in the context of the D-scoring method of measurement (DSM). Presented are three item fit statistics: mean absolute difference (MAD), mean absolute error (MAE), and root-mean-square error (RMSE). Regarding person fit, the following two statistics are presented: (a) Zd statistic―a DSM modification of the popular Z3 (or https://www.w3.org/1998/Math/MathML"> l z https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003343004/380a3502-ef76-465e-9732-50ba423d746f/content/CH07_equ_0001.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> ) statistic, and (b) Ud statistic―a DSM modification of the U3 statistic which measures the extent of fit between an observed response pattern and the expected Guttman pattern.
