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Measurement Quality

Test-Retest Reliability

Also called: retest reliability, temporal stability

Test-retest reliability measures how consistently an assessment ranks or scores people across two or more occasions when the underlying characteristic is expected to remain reasonably stable. It is commonly estimated with a correlation or agreement statistic. The result depends on the time interval, population, testing conditions, and whether real change is plausible.

Reviewed July 14, 2026 · 2 min read

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How it is estimated

The same assessment is administered to the same people at two points in time. Researchers then compare the scores. A strong relationship suggests people maintain a similar relative position, while an agreement analysis can test whether absolute values also remain close.

The interval matters. A retest after one hour may be inflated because people remember answers. A retest after several years includes genuine personality development and life changes. There is no universally correct interval.

Why results can differ

Differences can reflect measurement error, but not every difference is an error. Scores may change because of:

  • temporary mood, fatigue, or context;
  • learning or memory effects;
  • changed interpretation of an item;
  • genuine development in the measured trait;
  • a different device, language, or administration condition.

Researchers should choose conditions that match the intended interpretation.

Personality stability is not immobility

Personality traits are relatively enduring, not frozen. A useful personality assessment should show enough stability to support its claims while allowing real change. Strong retest reliability over a sensible interval supports precision; it does not prove construct validity.

Adaptive tests and retesting

An adaptive assessment may present different items during the second session. Retest evidence then evaluates whether the standardized algorithm and item bank produce comparable trait estimates, not whether every question is repeated.

Go deeper: Why personality-test results can change

Sources

Related terms

Test ReliabilityTest reliability is the consistency or precision of scores under specified conditions. A reliable assessment produces sufficiently similar results when the measured characteristic should be stable, or shows coherent evidence across relevant items. Reliability limits how confidently small score differences can be interpreted, but high reliability alone does not prove that the right construct is being measured.Internal ConsistencyInternal consistency describes how responses to items contributing to the same score relate to one another. It helps evaluate whether items behave as a coherent set, and is often summarized with coefficients such as Cronbach's alpha or omega. It does not show that a test is unidimensional, stable over time, or valid for its intended use.Personality TraitA personality trait is a relatively enduring tendency to think, feel, or behave in certain ways across time and situations. Traits are usually measured as dimensions, meaning people can fall anywhere along a continuum rather than belonging to a single fixed box. A trait score describes a tendency, not what someone will do in every circumstance.