A psychometric study of the Shipley Institute of Living Scale

A psychometric study was performed on the Shipley Institute of Living Scale to determine if it maintained an acceptable level of internal consistence reliability when used on a sample of 139 incarcerated sexual offenders in the Indiana Department of Correction. The study determined that the instrument did maintain an acceptable level of reliability on both subtests and for the entire test with reliability estimates above .80. An analysis of the next-item correlations was conducted in this study and it was determined that the average next-item correlation for Vocabulary was .17 and .38 for Abstraction. The analysis of the items on the Shipley Institute of Living Scale determined that, for this sample, the items may not have been set in an order that designates easiest to hardest items. A theoretical rearrangement of items served to improve the average next-item correlations on both subtests. The overall results of the study suggest that the SILS has good internal consistency reliability and should be used as a brief intellectual screen in a correctional setting. The results also suggest that further studies should be conducted on this instrument to determine if the instrument maintains similar reliability with other populations.