Definition
Cronbach’s Alpha is a statistical coefficient that measures the internal consistency of a multi-item scale—indicating how well individual items collectively measure a single underlying construct.

Introduction
When a survey contains multiple questions about the same idea, those questions should “agree” with one another. Cronbach’s Alpha tests whether the items within a scale behave like a harmonious choir or a dissonant mix.

Explanation
Developed by Lee Cronbach in 1951, the alpha value ranges from 0 to 1. A coefficient above 0.7 generally indicates acceptable reliability; above 0.8 signifies good internal consistency; and above 0.9 may suggest redundancy among items.
Mathematically, it assesses the average correlation among items. High alpha means that respondents who strongly agree with one statement (e.g., “I enjoy my work”) tend to respond similarly to related statements (“My job gives me satisfaction”).
However, a high alpha does not guarantee unidimensionality—factor analysis should verify that all items truly belong to one concept.

Key Takeaways
Cronbach’s Alpha is the heartbeat of survey reliability. It tells whether multiple questions sing the same tune of meaning.

Real-World Case
The Minnesota Satisfaction Questionnaire reports Cronbach’s alpha values above 0.85 for most subscales, confirming strong internal consistency in assessing job satisfaction worldwide.
Reference: https://www.apa.org