Cronbach's Alpha Calculator
Cronbach's alpha is the standard measure of a scale's internal consistency — how strongly a questionnaire's items hang together. Paste your response matrix (one row per respondent, one column per item) and get the raw α (the coefficient SPSS and R's psych::alpha report), the standardized α, the mean inter-item correlation and the full alpha-if-item-deleted table for item diagnostics. No SPSS licence, no syntax: results are verified against R's psych package. Common rules of thumb: α ≥ .9 excellent, ≥ .8 good, ≥ .7 acceptable — with the caveat that very high α can also signal redundant items. Your data stay in the browser.
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Let AI interpret your results: a downloadable Word document in APA 7 / business report format.
Frequently asked questions
How do I report Cronbach's alpha in APA 7 format?
Give the coefficient with the number of items, e.g.: "The 3-item scale showed good internal consistency, Cronbach's α = .93." When comparing items, cite the alpha-if-item-deleted values. The AI Report button writes the reliability paragraph — including item diagnostics — in APA 7 style.
What is an acceptable Cronbach's alpha?
The usual guideline: ≥ .70 acceptable for research use, ≥ .80 good, ≥ .90 needed for high-stakes individual decisions. Below .70, check the alpha-if-item-deleted table for weak items. Note that α also rises mechanically with more items, and α > .95 may indicate redundancy rather than quality.
What does alpha-if-item-deleted tell me?
It recomputes α with each item removed in turn. If deleting an item would raise α noticeably above the current value, that item correlates poorly with the rest of the scale and is a candidate for revision or removal — balance this against content coverage before dropping items.
What is the difference between raw and standardized alpha?
Raw α works on the item covariances (what SPSS reports as "Cronbach's Alpha"); standardized α works on correlations, as if all items were z-standardized. They differ when item variances are unequal. Report raw α unless you actually sum standardized items.