Re: cronbach alpha for binary responses

Posted by Baker, Harley on Dec 30, 2009; 7:39am
URL: http://spssx-discussion.165.s1.nabble.com/cronbach-alpha-for-binary-responses-tp1086058p1086069.html

Eins,

Actually, with dichotomous data, coefficient alpha is mathematically
equivalent to KR-20, which calculates the internal consistency of a scale
composed of dichotomous items. As a reviewer for a couple of journals, my
recommendation is to use coefficient alpha.

Harley

Dr. Harley Baker
Professor and Chair, Psychology Program
Sage Hall 2061
California State University Channel Islands
One University Drive
Camarillo, CA 93012

805.437.8997 (p)
805.437.8951 (f)

[hidden email]

> From: "Steve Simon, P.Mean Consulting" <[hidden email]>
> Reply-To: "Steve Simon, P.Mean Consulting" <[hidden email]>
> Date: Tue, 29 Dec 2009 11:07:15 -0600
> To: <[hidden email]>
> Subject: Re: cronbach alpha for binary responses
>
> Eins Bernardo wrote:
>
>> May I know if Cronbach alpha can be used as measure of reliability for a
>> correct/wrong response (coded 0 or 1) items?  I want to use it for each
>> subscale (with 8 items each) of my instrument with three scales.  Thank
>> you for your comments.
>
> PASW Statistics/SPSS will allow you to calculate Cronbach's alpha for
> this type of data, but the more important question is whether you can
> get those results published. As far as I know, Cronbach's alpha does not
> make any distributional assumptions. There may be problems with
> artificial bounds being placed on Cronbach's alpha by the discrete
> nature of your data. This might make it impossible for this measure to
> get very close to +1, depending on the degree of skewness of your binary
> variables.
>
> I suspect that your peer reviewers would give you a hard time about this
> measure, although there isn't much in the way of alternatives available
> here. I wouldn't fuss about it, but I am rarely asked to be a
> peer-reviewer.
>
> It costs nothing other than a few electrons to make the calculation. So
> put it in, mention the binary nature of your data as a limitation and
> see what the peer-reviewers say.
>
> I hope this helps.
> --
> Steve Simon, Standard Disclaimer
> "The first three steps in a descriptive
> data analysis, with examples in PASW/SPSS"
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