Top-down purification of Tobacyk's Revised Paranormal Belief Scale

Using mostly undergraduate student data (N = 560), factor analysis confirme d the existence of seven factors in Tobacyk's Revised Paranormal Belief Sca le (RPBS). However. this replication proved to be of dubious value since (1 ) the factor structure was significantly affected by age and gender; (2) th e items in Tobacyk's original factors were significantly non-additive; (3) the items showed pervasive differential item functioning (DIF) related to r espondents' ages, gender, or both; and (4) simulations indicated that the f actor structure are the result of DIF. The removal of DIF via "top-down pur ification" yielded two correlated clusters of items dubbed "New Age Philoso phy" and "Traditional Paranormal Beliefs". Both clusters obey an Andrich ra ting-scale model with person reliabilities of 0.90 and 0.74, respectively. Principal component analysis confirmed that these two clusters are unidimen sional and without significant age or gender DIF (p > 0.10), While the Trad itional Paranormal Beliefs cluster continued to show a significant main eff ect of age, neither cluster showed a significant gender effect, thereby cal ling into question some traditional findings regarding paranormal beliefs. We strongly suspect that the dearth of DIF studies indicates that age and g ender biases due to DIF have largely gone unnoticed in the extant personali ty and assessment literature. (C) 2000 Elsevier Science Ltd. All rights res erved.