October 2008 home | PDF | SWF |

Title
An Attempt to Fit the Rasch Model to a C-Test

Author
Purya Baghaei

Bio Data:
Purya Baghaei is an assistant professor in the English Department of Islamic Azad University, Mashad, Iran. His main research interests are language testing and the application of Rasch modelling in social science research.

Abstract
There are a number of powerful statistical techniques and analyses within the Rasch model that provide evidence for test validity. The quality control fit statistics, principal component analysis of residuals and differential item functioning (DIF) are among the techniques offered by Rasch measurement for test validation. In this study these three analyses are applied to a C-Test to demonstrate its construct validity. The results show that the C-Test deviated from unidimensionality principal. It is therefore concluded that every C-Test battery requires rigorous empirical research for construct validity before it is used for practical testing purposes.

Key words: Rasch model, construct validity, probability of a right answer

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