What does Cronbach's alpha measure?

What does Cronbach's alpha measure?

• A. internal consistency reliability
• B. test-retest reliability
• C. inter-rater reliability
• D. construct validity

Answer: (A)

Cronbach's alpha measures internal consistency reliability. It reflects how well the items on a scale work together to assess the same underlying construct, by looking at how consistently they correlate with one another. When items tap the same thing, respondents’ answers tend to move together, producing a higher alpha. Interpreting the value: scores range from 0 to 1. A higher alpha indicates stronger inter-item agreement, suggesting the scale is measuring a coherent construct. Common guidelines view around 0.70 or higher as acceptable, 0.80 or higher as good, and values above 0.90 as excellent (though very high values can hint at item redundancy). This statistic is not about stability over time (that would be test-retest reliability), not about agreement between different raters (inter-rater reliability), and not a direct measure of whether the scale actually captures the intended construct (validity). It is also affected by the number of items on the scale—the more items, the more likely alpha will inflate, sometimes without meaningful increases in true reliability. It’s wise to check that items are conceptually related and to consider factor analysis to assess dimensionality before relying on alpha as the sole reliability judge.

Cronbach's alpha measures internal consistency reliability. It reflects how well the items on a scale work together to assess the same underlying construct, by looking at how consistently they correlate with one another. When items tap the same thing, respondents’ answers tend to move together, producing a higher alpha.

Interpreting the value: scores range from 0 to 1. A higher alpha indicates stronger inter-item agreement, suggesting the scale is measuring a coherent construct. Common guidelines view around 0.70 or higher as acceptable, 0.80 or higher as good, and values above 0.90 as excellent (though very high values can hint at item redundancy).

This statistic is not about stability over time (that would be test-retest reliability), not about agreement between different raters (inter-rater reliability), and not a direct measure of whether the scale actually captures the intended construct (validity). It is also affected by the number of items on the scale—the more items, the more likely alpha will inflate, sometimes without meaningful increases in true reliability. It’s wise to check that items are conceptually related and to consider factor analysis to assess dimensionality before relying on alpha as the sole reliability judge.