Which statement best describes Cronbach's alpha?

• A. A measure of test-retest reliability
• B. A measure of internal consistency
• C. A measure of inter-rater reliability
• D. A measure of face validity

Answer: (B)

Cronbach's alpha measures internal consistency, showing how well the items on a scale hang together to tap the same construct. It reflects how closely related the items are and how reliably they combine into a single score. A higher alpha means the items correlate well with each other and with the total score, suggesting the scale is a coherent measure. This is different from test-retest reliability, which looks at score stability over time, inter-rater reliability, which concerns agreement among different raters, and face validity, which is about whether the items appear to measure what they’re intended to measure. Values typically range from 0 to 1, with common benchmarks around 0.70 for basic research and higher for clinical decisions; very high values may indicate redundant items. Remember that Cronbach's alpha assumes the scale is unidimensional and can be influenced by the number of items, so a very long scale can inflate alpha even if inter-item correlations are modest.