Confidence intervals for a sample Cronbach coefficient alpha value

n (sample size):
The number of items in the measure (often called "k"):
The oserved alpha value:
Confidence interval you want (usually 95%):
Decimal places you want for the answers:
This program runs within R ( R is a brilliant open source (i.e. free) statistics package derived from S and related to the equally excellent but not cheap commercial product S+ (

11.xi.17: For an example of how useful the CI around Cronbach's alpha is a diagnostic of problems, for example in cross-cultural research, you can see my paper: Evans, Dolan and Toriola (1997) Detection of intra- and cross-cultural non-equivalence by simple methods in cross-cultural research: evidence from a study of eating attitudes in Nigeria and Britain Eating and Weight Disorders 2:67-78. I am mounting it here as the publishers have lost it!!! See this page for the odd history and to download the paper.

Please also note that I accept no responsibility for this script's results. I have enormous faith in R and programming this was trivial but if anything major depends on this, then you need to pay for good statistical support locally.

If you do find an error or problems here tell me!
All access is logged for IP address, time/date and parameters entered so I can track any abuse of the server.

Licensing and copying
You can download script that runs this

You will need to understand a bit about R and have David Firth's CGIwithR package to make the script or a derivative of it work on your own server.

Like almost everything on this website this work is licensed under a Creative Commons License.

Creative Commons License