Item analysis of the subscales in the Eight State Questionnaire (8SQ): Exploratory and confirmatory factor analyses
Boyle, G. J. (1991). Item Analysis of the Subscales in the Eight State Questionnaire (8SQ): Exploratory and Confirmatory Factor Analyses. Multivariate Experimental Clinical Research, 10(1), 37-65.
The Eight State Questionnaire (8SQ) is a comprehensive self-report inventory which has been used in numerous studies of multidimensional mood states. The 8SQ has been useful in clinical situations for evaluating the efficacy of various therapeutic interventions, as well as in other contexts. The instrument takes about 20-25 minutes to administer, thereby enhancing its usefulness as a quick measure of transitory, constantly fluctuating mood states. Nevertheless, examination of the congeneric factor structure of the 8SQ subscales suggests that a number of the items are complex, contributing significantly to more than one subscale dimension. Both exploratory and confirmatory factor analyses have failed to provide substantial support for the existing subscale structure. Hence, further research should be directed toward refining the 8SQ item composition, by replacing items which contribute inadequately to the respective subscales, and/ or those which are factorially complex. Such "progressive rectification" (Cattell's term) should result in a more psychometrically efficient instrument, which is characterized by greater factor purity and reduced intercorrelations, than is currently evident.