What is the term for a hypothetical score based on no measurement error, which can be estimated but not precisely known?

The term that relates to a hypothetical score based on no measurement error is referred to as the true score. In psychometrics, the true score represents the actual ability or trait level of an individual, free of any errors that might arise in the measurement process. This concept is essential when considering the reliability of assessments, as it serves as a benchmark for understanding what an individual's score would ideally reflect if it were untainted by various forms of error, such as random fluctuations, biases in the test items, or other influences that could affect performance.

The true score is estimated through various statistical methods, often involving the assumption that observed scores can be decomposed into true scores and measurement errors. However, because measurement errors can vary from test to test and context to context, the true score cannot be known with absolute precision. Instead, it is inferred from observed scores, allowing researchers and evaluators to explore the range of potential true scores that an individual might have based on their assessment results.

This distinction is crucial in research and program evaluation because the accuracy of evaluations improves by recognizing and aiming to minimize measurement errors that distort observed scores. Understanding the concept of true score enhances the interpretation of scores and drives better decision-making in psychological testing and educational assessments.