Wright's residual-based person fit indices were the first person fit indices with dichotomous IRT model and commonly used with Rasch model software. Although there were number of studies which suggested modifications to improve the statistical properties of the Wright's indices, they remained to lack good statistical properties.The study presented a new person fit index and how it can be interpreted and applied for detecting person misfit. Moreover, through a simulated data, the study investigated the statistical properties and the power rates of the new index and compared it with Wright's indices. Results showed that the new index had superior statistical properties under different test conditions and overcome the Wright's index.

Wright's residual-based person fit indices were the first person fit indices with dichotomous IRT model and commonly used with Rasch model software. Although there were number of studies which suggested modifications to improve the statistical properties of the Wright's indices, they remained to lac...