Some papers also offered indications of alpha having a threshold or cut-off as an acceptable, sufficient or satisfactory level. This was normally seen as ≥0.70 (five instances) or >0.70 (three instances) although one article more vaguely referred to “the acceptable values of 0.7 or 0.6” (Griethuijsen et al., 2014).
alpha values were described as
excellent (0.93–0.94),
strong (0.91–0.93),
reliable (0.84–0.90),
robust (0.81),
fairly high (0.76–0.95),
high (0.73–0.95),
good (0.71–0.91),
relatively high (0.70–0.77),
slightly low (0.68),
reasonable (0.67–0.87),
adequate (0.64–0.85),
moderate (0.61–0.65),
satisfactory (0.58–0.97),
acceptable (0.45–0.98),
sufficient (0.45–0.96),
not satisfactory (0.4–0.55)
low (0.11). (Taber, 2016).
Many sources say above 0.70 is acceptable. 0.80 or greater is preferred. Higher is better.
Source: Cortina, J. M. (1993). What is coefficient alpha? An examination of theory and applications. Journal of applied psychology, 78(1), 98.
Dear Danilo,
Here are some details on the alpha coefficient
Alpha coefficient / implied reliability
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
With my best regards
Prof. Bachir ACHOUR
Dear Danilo,
Cronbach's alpha measures the internal consistency or reliability of a data set; this is one of the considerations to judge the suitability of a data set for statistical analysis (e.g. factor analysis). Other tests that also measure the internal consistency of data are Split-half reliability, and Odd-even reliability.
Prof. Bachir ACHOUR has rightly mentioned the ranges of Cronbach's alpha coefficients and the implied reliability. The detailed information on the topic. Thanks to Prof. Achour.
One question to Prof. Achour: > 0.90, - I think this indicates too much inter-relations i.e. data redundancy and not acceptable. Is it right?
Best wishes
Dear Asit,
Thank you for your appreciation. Yes, your are right regarding alpha coefficient greater than 0.90. I'm agree with you.
With my best regards
Prof. Bachir ACHOUR
Some papers also offered indications of alpha having a threshold or cut-off as an acceptable, sufficient or satisfactory level. This was normally seen as ≥0.70 (five instances) or >0.70 (three instances) although one article more vaguely referred to “the acceptable values of 0.7 or 0.6” (Griethuijsen et al., 2014).
alpha values were described as
excellent (0.93–0.94),
strong (0.91–0.93),
reliable (0.84–0.90),
robust (0.81),
fairly high (0.76–0.95),
high (0.73–0.95),
good (0.71–0.91),
relatively high (0.70–0.77),
slightly low (0.68),
reasonable (0.67–0.87),
adequate (0.64–0.85),
moderate (0.61–0.65),
satisfactory (0.58–0.97),
acceptable (0.45–0.98),
sufficient (0.45–0.96),
not satisfactory (0.4–0.55)
low (0.11). (Taber, 2016).
For clear understanding and application, a simple and accepted classification (Cronbach's alpha values) is required.
Some statisticians also agree the Cronbach Alpha value if they are .6, is this correct?
In the analysis of the scales. Do you perform analysis of the scales after transforming the reverse (negative) questions? When I analyse before transforming the reverse questions my Alpha becomes 0.73 but after transforming the questions it rises to 0.75....
help please!!!
You should absolutely reverse-score and reverse-worded items before assessing alpha. (Consider that alpha is a function of the average inter-item correlation, so if some correlations are negative...) The fact that the estimates of alpha that you obtain are so similar whether you do or do not reverse-score is troubling, unless you have so many items, and just a few a reverse scored, in which case they just don't matter much
Saul Shiffman thank you so much for your educative answer and time. Be blessed.
with thanks,
Mohamed
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