Cronbach's Alpha Calculator
Estimate Cronbach's Alpha, a measure of internal consistency reliability, from the number of test items and average inter-item correlation.
Average of all pairwise item correlations
Cronbach's Alpha
0.896
Reliability Level7
Cronbach's Alpha vs Number of Test Items
How Cronbach's Alpha Works
Cronbach's Alpha estimates reliability based on the number of items and their average correlation. Higher alpha means the items consistently measure the same construct.
Standardized Alpha Formula
Alpha = (k x r_avg) / (1 + (k - 1) x r_avg)
Where k is the number of items and r_avg is the average inter-item correlation.
Interpretation
Example Calculation
A 20-item survey has an average inter-item correlation of 0.30.
- 01Numerator: 20 x 0.30 = 6.0
- 02Denominator: 1 + (20 - 1) x 0.30 = 1 + 5.7 = 6.7
- 03Alpha = 6.0 / 6.7 = 0.896
- 04Interpretation: Good reliability (0.80-0.89)