Summed versus estimated factor scores: Considering uncertainties when using observed scores.

Observed scores (e.g., summed scores and estimated factor scores) are assumed to reflect underlying constructs and have many uses in psychological science. Constructs are often operationalized as latent variables (LVs), which are mathematically defined by their relations with manifest variables in an LV measurement model (e.g., common factor model). We examine the performance of several types of observed scores for the purposes of (a) estimating latent scores and classifying people and (b) recovering structural relations among LVs. To better reflect practice, our evaluation takes into account different sources of uncertainty (i.e., sampling error and model error). We review psychometric properties of observed scores based on the classical test theory applied to common factor models, report on a simulation study examining their performance, and provide two empirical examples to illustrate how different scores perform under different conditions of reliability, sample size, and model error. We conclude with general recommendations for using observed scores and discuss future research directions. (PsycInfo Database Record (c) 2026 APA, all rights reserved).