Cronbach Alpha Reliability Calculator
Compute Cronbach alpha, the most widely used measure of internal consistency reliability for a psychometric scale.
How to Use the Cronbach Alpha Reliability Calculator
- Enter the number of scale items K.
- Enter the sum of individual item variances.
- Enter the total scale variance.
- Click Calculate.
Casos de Uso
- •Survey and questionnaire validation.
- •Psychometrics course work.
- •HR assessment tool review.
Fórmula
α = K / (K − 1) × (1 − Σσ²_i / σ²_total), where K is the number of items, σ²_i the variance of each item and σ²_total the total scale variance.
Preguntas Frecuentes
How do I interpret α?
Common heuristics: <0.6 poor, 0.6–0.7 questionable, 0.7–0.8 acceptable, 0.8–0.9 good, ≥0.9 excellent. Some fields (diagnostics) demand ≥0.9.
Does high alpha imply a single construct?
No. Alpha only measures internal consistency — unidimensionality needs factor analysis. Very high α (>0.95) may indicate redundant items.
Medical disclaimer
Educational only. Psychometric scale development for clinical use should follow full validation procedures including factor analysis and test-retest reliability.