The degree to which observed values or scores are free from errors of measurement refers to

Freedom of observed scores from measurement error refers to reliability.

A reliable measure yields consistent, repeatable results across occasions.

Content validity concerns how well items cover the whole domain, not error freedom.

Construct validity is how well a test measures the intended theoretical trait.

Criterion validity is agreement of a test with an external outcome standard.

Observed score equals true score plus error in classical test theory.