Cronbach's Alpha Calculator (Scale Reliability)
How internally consistent is my questionnaire scale?
Spec sheet
cronbach_1951 · v1.0.0Cronbach's alpha (1951)
- 01
α = k/(k − 1) · (1 − Σ σ²_item / σ²_total) - 02
sample variances (n − 1) - 03
α if item deleted: recompute without that item
- Assumes a unidimensional scale with tau-equivalent items; consider McDonald's omega otherwise.
- Respondents with missing answers must be removed first.
- Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16, 297–334standard
Worked example
computed by the same formula8 respondents × 5 Likert items
- Scores — one line per respondent, one column per item
- 4 5 4 3 4 3 3 4 2 3 5 5 5 4 5 2 3 2 2 3 4 4 5 3 4 3 4 3 3 3 5 4 5 5 4 2 2 3 1 2
- Cronbach's α
- 0.95
- Items
- 5
- Respondents
- 8
- Removing this item raises α most
- Item 3 (α → 0.951)
Questions
How is the cronbach's alpha calculator calculated?
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Cronbach's alpha (1951). α = k/(k − 1) · (1 − Σ σ²_item / σ²_total) · sample variances (n − 1) · α if item deleted: recompute without that item
Example: 8 respondents × 5 Likert items?
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Cronbach's α: 0.95; items: 5.
What does this calculator not cover?
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Assumes a unidimensional scale with tau-equivalent items; consider McDonald's omega otherwise. Respondents with missing answers must be removed first.
Where do the numbers come from?
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Sources: Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16, 297–334. The formula is versioned (cronbach_1951 v1.0.0) and covered by automated tests.
Is my data stored?
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No. The calculation runs in your browser and nothing is sent unless you choose to save a shareable link.
Also searched ascronbach alpha calculator · scale reliability · internal consistency questionnaire · likert scale reliability · alpha if item deleted