Cronbach's Alpha
Statistics & analysis
Definition
A coefficient (0–1) estimating the internal-consistency reliability of a multi-item scale; values of 0.7 and above are commonly considered acceptable.
Alpha asks a simple question: do the items of a scale move together enough to be treated as one measure? It rises with inter-item correlation and with the number of items — which also means a long scale can score well while containing weak items.
Convention treats 0.70 as acceptable and 0.80+ as good, but alpha above ~0.95 can signal redundant items. Report alpha per construct in your instrument section, and check 'alpha if item deleted' before dropping anything.
Where it's used
- Establishing questionnaire reliability before hypothesis testing
- Reporting scale quality in the instrumentation section of a thesis
- Pilot-study checks before full data collection
Software used
SPSSSmartPLSRJASP
Related concepts
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