Crohnbach’s alpha

This measures the internal consistency on a scale. It is often used when you have multiple Likert questions in a questionnaire that form a scale and you wish to test the reliability of the scale. Example is when the answer of a question range from “strongly agree” to “strongly disagree”.

Procedure

1. Click Analyze– Scale– choose Reliability Analysis
2. Transfer the variables into the Items box.

3. Leave the model set as “Alpha”, this represents Crohnbach’s alpha, you can choose the name of your scale in the Scale label
4. Click the Statistic button to open the Reliability Analysis dialogue box
5. Select the Item, Scale, Scale if item delete, and Correlation
6. Click the Continue button
7. Click Ok to generate the output.

From the reliability statistic table, A high value of Crohnbach’s alpha indicates a high level of internal consistency. The item-total-statistic table shows the value of Crohnbach’s alpha if the particular item was deleted.