A Comparison of Classical and Latent Trait Item Analysis Procedures

Abstract

Several methods of psychometric instrument construction have been suggested in the literature. Although there is considerable information describing theoretical and mathematical differences among these methods, there is a paucity of data regarding actual differences resulting from practical applications. Therefore, the present study was designed to compare classical item analysis procedure with the Rasch latent trait analysis in terms of several applied concerns. Respondents were 373 predominately white university undergraduates who completed the MacAndrew alcoholism scale and the Khavari Alcohol Test, an instrument for assessing quantity-frequency of alcohol consumption. Responses to the MacAndrew scale were analyzed using both classical and Rasch procedures and the resulting sub-scales were then compared in terms of specific items selected, relationship to the full scale, and assessment of actual alcohol consumption. Results showed substantial differences between the two procedures in terms of selected items. Several items were selected by the Rasch procedure but rejected by the classical procedure and vice versa. However, items selected by these procedures appear to make little difference in terms of correlations with the original full scale or with a criterion measure. Thus, due to its simplicity, classical item analysis may be indeed a procedure of choice if some type of item analysis is deemed necessary for clinical instruments.