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Generalizability theory (GT) provides an all-encompassing framework for estimating accuracy of scores and effects of multiple sources of measurement error when using measures intended for either norm- or criterion-referencing purposes. Structural equation models (SEMs) can replicate results from GT-based ANOVA procedures while extending those analyses to account for scale coarseness, generate Monte Carlo-based confidence intervals for key parameters, partition universe score variance into general and group factor effects, and assess subscale score viability. We apply these techniques in R to univariate, multivariate, and bifactor designs using a novel indicator-mean approach to estimate absolute error. When representing responses to items from the shortened form of the Music Self-Perception Inventory (MUSPI-S) using 2-, 4-, and 8-point response metrics over two occasions, SEMs reproduced results from the ANOVA-based mGENOVA package for univariate and multivariate designs with score accuracy and subscale viability indices within bifactor designs comparable to those from corresponding multivariate designs. Adjusting for scale coarseness improved the accuracy of scores across all response metrics, with dichotomous observed scores least approximating truly continuous scales. Although general-factor effects were dominant, subscale viability was supported in all cases, with transient measurement error leading to the greatest reductions in score accuracy. Key implications are discussed.
Vispoel et al. (Wed,) studied this question.