The intolerance of uncertainty scale: measurement invariance, population heterogeneity, and its relation with worry among self-identifying White and Black respondents.

Although it is understood that assessment tools require evaluation using diverse samples, such evaluations are relatively rare. There are obstacles to such work, but it remains important to pursue psychometric data in broad samples. As such, we evaluated measurement invariance and population heterogeneity of two versions of a widely used measure in the anxiety literature--the Intolerance of Uncertainty Scale (IUS)--among self-identifying White (N = 1,185) and Black (N = 301) students. Data from multiple-groups confirmatory factor analysis supported the equivalence of the equal form and factor loadings of both IUS versions in White and Black respondents. However, specific IUS items functioned differently in the two groups, with more IUS items appearing biased in the full-length relative to the short-form version. Correlations between IUS factors and worry were equivalent among White and Black respondents. We discuss the implications of these results for future research.