Cronbach Alpha Calculator

Formula

The formula to calculate Cronbach Alpha is:

\[ \alpha = \frac{N \times C}{v + (N - 1) \times C} \]

Where:

\(\alpha\) is the coefficient alpha
\(N\) is the number of items
\(C\) is the covariance between item pairs
\(v\) is the average covariance

What is Cronbach Alpha?

Cronbach’s alpha, also known as coefficient alpha, is a measure of the internal consistency of a test. In other words, it assesses how reliable the test is at predicting an outcome. A higher Cronbach’s alpha indicates greater reliability.

Example Calculation 1

Let's assume the following values:

Number of Items (N) = 10
Covariance between Item Pairs (C) = 0.5
Average Covariance (v) = 0.3

Using the formula:

\[ \alpha = \frac{10 \times 0.5}{0.3 + (10 - 1) \times 0.5} = \frac{5}{0.3 + 4.5} = \frac{5}{4.8} \approx 1.04 \]

The Cronbach Alpha is approximately 1.04.

Example Calculation 2

Let's assume the following values:

Number of Items (N) = 5
Covariance between Item Pairs (C) = 0.4
Average Covariance (v) = 0.2

Using the formula:

\[ \alpha = \frac{5 \times 0.4}{0.2 + (5 - 1) \times 0.4} = \frac{2}{0.2 + 1.6} = \frac{2}{1.8} \approx 1.11 \]

The Cronbach Alpha is approximately 1.11.