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What is an acceptable level of reliability for a psychometric test?

Most psychological societies (e.g., British Psychological Society) and academics (e.g., Devellis, 1991) suggest that an acceptable level of reliability for psychometric tests is:

Ability/Aptitude Tests: .80

Personality Tests: .70


Acceptable and unacceptable levels of the Cronbach’s Alpha coefficient

below .60: unacceptable

between .60 and .65: undesirable

between .65 and .70: minimally acceptable

between .70 and .80: respectable

between .80 and .90: very good

much above .90: consider shortening the scale


DeVellis, R.F. (1991). Scale development. Newbury Park, NJ: Sage Publications.
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