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