Invariance: What Does Measurement Invariance Allow Us to Claim?

Abstract

Measurement involves numerous theoretical and empirical steps-ensuring our measures are operating the same in different groups is one step. Measurement invariance occurs when the factor loadings and item intercepts or thresholds of a scale operate similarly for people at the same level of the latent variable in different groups. This is commonly assumed to mean the scale is measuring the same thing in those groups. Here we test the assumption of extending measurement invariance to mean common measurement by randomly assigning American adults (N = 1500) to fill out scales assessing a coherent factor (search for meaning in life) or a nonsense factor measuring nothing. We find a nonsense scale with items measuring nothing shows strong measurement invariance with the original scale, is reliable, and covaries with other constructs. We show measurement invariance can occur without measurement. Thus, we cannot infer that measurement invariance means one is measuring the same thing, it may be a necessary but not a sufficient condition.