Abstract

The Leyton Obsessional Inventory(Cooper, 1970) was modified into a paper-and-pencil form to facilitate its group administration. Verification of reliability, validity and factor structure was carried out on the modified version replies of 426 students(middle school students ; 140, high school students ; 126, college students ; 160). Cronbach's alpha-coefficient was used to calculate the internal consistency of the inventory, and turned out to be .86. The same consistency index was calculated for each of the four subscales. In this case, the alpha coefficients were .84(symptom), .61(trait), .84(resistance), and .86(interference). For the test-retest results with one week interval, the product-moment correlation coefficients were .80(symptom), .83(trait), .86(resistance), .86(interference), and .84(total). Validity was evaluated using scores of the LOI measures and scores of SCL-90-R. Correlations of the LOI measures and SCL-90-R measure were .25(symptom), .12(trait), .32(resistance), .33(interference), and .22(total). Subjects' responses to the inventory were studied by factor analysis. The principal-component method was used, with repetitions followed by Varimax rotation. Eight factors were identified, explaining 63.4% of the variance. These factors may be described as follows ; I : Order and tidiness, II : Perfectionism, III : Dirt and contamination, IV : Repetition, V : Checking, VI : Cleanliness, VII : Unpleasant anticipation, VIII : Cautiousness. The requirement of further study for the standardization and development of LOI short-form and child version were emphasized.