Cronbach’s Alpha (α)

A Psychometric measure of internal consistency

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

AKA

• Coefficient Alpha (α)

• Cronbach’s alpha (α) is a measure of the internal consistency of multiple items or questions within a single survey
• Used for surveys/questionnaires

Scoring

Values range from 0.00 (not reliable) to 1.00 (perfectly reliable)

“Rule of thumb” Quick interpretation of reliability

Score	Reliability
0.00 – 0.20	Poor
0.21 – 0.40	Fair
0.41 – 0.60	Moderate
0.61 – 0.80	Good
0.81 – 1.00	Excellent

Scoring

Interpretation

• You want internal consistency results (i.e. Cronbach’s Alpha (α)) to be high, we do not want it to be too high.
• An (α) greater than about 0.90 may indicate unnecessary redundancy among the items and means that some of them can be eliminated without jeopardizing the reliability of the scale.