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Psychometrics & Testing

Test-Retest Reliability

Whether a test produces consistent scores when the same person takes it twice. Measures temporal stability of the construct.

Test-retest reliability (APA Standards, 2014) measures: if you take the test today and again in 2 weeks, how similar are the scores? High test-retest reliability (r=0.80+) means the test is stable and measuring a stable trait.

Example: Big Five personality tests typically have test-retest reliability of r=0.70-0.85 over 2-4 weeks (personality is relatively stable). IQ tests have even higher test-retest reliability (r=0.90+, IQ is very stable). Depression screening scales have lower test-retest reliability (r=0.60-0.70) because mood fluctuates.

Test-retest reliability differs from internal consistency (Cronbach's alpha). High internal consistency means items correlate with each other (measuring one thing). High test-retest reliability means the score is stable over time.

For personality: high test-retest reliability validates that personality is stable. For mood assessments: moderate test-retest reliability is expected (mood changes). If you retake a personality test and get drastically different results, either the test is unreliable or you've genuinely changed.

Source: APA Standards; Cronbach, L. J. (1960) Essentials of Psychological Testing.

Related Terms

Validity (Psychometric)
Whether a test measures what it claims to measure. A valid personality test actually predicts real-world outcomes like job performance, relationship satisfaction, or mental health.
Likert Scale
A response format used in personality tests where you rate agreement on a scale (e.g., "Strongly Disagree" to "Strongly Agree"). Named after psychologist Rensis Likert (1932).
Psychometric Test
A standardized, scientifically designed assessment that measures psychological attributes, personality traits, cognitive abilities, aptitudes, or attitudes, in a reliable and valid way.
Cronbach's Alpha
A statistical measure of internal consistency reliability. Values range 0-1; α=0.70-0.90 is ideal for personality tests. Indicates whether scale items correlate with each other.
Normal Distribution (Bell Curve)
A statistical pattern where most values cluster around the average, with fewer values at the extremes. Personality traits follow this pattern, most people score near the middle.
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