Overestimation of Internal Consistency by Coefficient Omega in Data Giving Rise to a Centroid-Like Factor Solution.

Coefficient Omega measuring internal consistency is investigated for its deviations from expected outcomes when applied to correlational patterns that produce variable-focused factor solutions in confirmatory factor analysis. In these solutions, the factor loadings on the factor of the one-factor measurement model closely correspond to the correlations of one manifest variable with the other manifest variables, as is in centroid solutions. It is demonstrated that in such a situation, a heterogeneous correlational pattern leads to an Omega estimate larger than those for similarly heterogeneous and uniform patterns. A simulation study reveals that these deviations are restricted to datasets including small numbers of manifest variables and that the degree of heterogeneity determines the degree of deviation. We propose a method for identifying variable-focused factor solutions and how to deal with deviations.