Asymptotic Standard Errors for Reliability Coefficients in Item Response Theory

Reliability is a crucial index of measurement precision and is commonly reported in substantive research using latent variable measurement models. However, reliability coefficients, often treated as fixed values, are estimated from sample data and thus inherently subject to sampling variability. Building on the recently proposed regression framework of reliability (Liu, Pek, & Maydeu-Olivares, 2025), this study classifies reliability coefficients in item response theory (IRT) into classical test theory (CTT) reliability and proportional reduction in mean squared error (PRMSE) and derives their asymptotic standard errors (SEs) to quantify this variability. Unlike existing approaches (e.g., Andersson & Xin, 2018), which requires computing population moments, we focus on cases using sample moments instead. This allows for estimation of reliability and SEs in long tests. By incorporating sampling variability arising from both item parameter estimation and the use of sample moments, we present a more general strategy for computing SEs of model-based reliability coefficients. Simulation results confirm that the derived SEs accurately capture the sampling variability across various test lengths in moderate to large samples.