Internal structure and criterion relationships for long and brief versions of the intratextual fundamentalism scale (IFS) among israeli jews

The Intratextual Fundamentalism Scale (IFS; Williamson & Hood, 2005) was designed to measure religious fundamentalism. Published analyses of the IFS-12 and various short forms have revealed potential issues with its psychometric fitness. For the present paper, we used bifactor confirmatory factor analysis, dimensionality measures (e.g., explained common variance), and model-based reliability estimates (e.g., ω hierarchical) to provide a more detailed examination of the dimensionality of the IFS-12 and the reliability of its raw total score among 432 Israeli Jews. Results indicated that the instrument is unidimensional enough to permit the use of a unidimensional solution when modeling the instrument. The IFS-12's raw total score was also found to predominantly reflect a single general Intratextual Fundamentalism factor, despite the presence of minor multidimensionality across items, which provides support for the reliability of this score. This conclusion was further supported by the results from structural regression-parameter bias tests: the decision to model the IFS-12 as a unidimensional instrument rather than a bifactor instrument did not alter the strength of the association between the general latent Intratextual Fundamentalism factor or any of the latent Big-5 personality trait factors. Last, because the IFS-12 demonstrated poor global fit when modeled as a unidimensional instrument, we used individual explained common variance (IECV) coefficients to develop a short form: the IFS-6. Reliability evidence and internal unidimensional structure and content-oriented and concurrent evidence of validity are presented for the IFS-6 total score. The importance of follow-up research on the generalizability of these IFS-12, IFS-6, and IFS-5 results across populations is discussed.