Chronbach’s Alpha is a way to measure the internal consistency of a questionnaire or survey.
Cronbach’s Alpha ranges between 0 and 1, with higher values indicating that the survey or questionnaire is more reliable.
When reporting the value of Cronbach’s Alpha in a final report, you need to include the following two values:
- The number of items used on the subscale.
- The value of Cronbach’s Alpha.
The following examples show how to report Cronbach’s Alpha in different situations.
Example 1: Reporting Cronbach’s Alpha for One Subscale
Suppose a restaurant manager wants to measure overall satisfaction among customers. She decides to send out a survey to 200 customers who can rate the restaurant on a scale of 1 to 5 for 12 different categories.
When she receives the results of the survey, she finds that the value for Cronbach’s Alpha is 0.84.
Here is how she would report Cronbach’s Alpha in a formal write-up:
A satisfaction survey was sent to 200 customers. The survey consisted of 12 items and the value for Cronbach’s Alpha for the survey was α = .84.
Example 2: Reporting Cronbach’s Alpha for Multiple Subscales
Suppose a Human Resources manager at a company sends out a three-part questionnaire to all 500 employees at the company.
When she receives the results of the survey, she calculates the value for Cronbach’s Alpha for all three of the subscales.
Here is how she would report the value of Cronbach’s Alpha in a formal write-up:
A three-part questionnaire was sent to 500 employees. The agreeableness subscale consisted of 10 items (α = .65), the leadership subscale consisted of 12 items (α = .82), and the overall satisfaction subscale consisted of 14 items (α = .88).
The following table describes how different values of Cronbach’s Alpha are usually interpreted:
|Cronbach’s Alpha||Internal consistency|
|0.9 ≤ α||Excellent|
|0.8 ≤ α < 0.9||Good|
|0.7 ≤ α < 0.8||Acceptable|
|0.6 ≤ α < 0.7||Questionable|
|0.5 ≤ α < 0.6||Poor|
|α < 0.5||Unacceptable|
When reporting the value of Cronbach’s Alpha for a given scale or survey, you can reference this table to determine if the value is at least considered “acceptable” or not.