[R] omega vs. alpha explanation

[Bert Gunter]

Advice:

Do not post here. This does not appear to be an R question. Post to a
statistics list like stats.stackexchange.com instead.

-- Bert

On Wed, Oct 10, 2012 at 6:42 AM, codec cat <v.codecat at gmail.com> wrote:
> Dear all
>
> I wonder if someone can explain what is the main difference between omega
> and alpha reliabilities?
>
> I understand an omega reliability is based on hierarchical factor model as
> shown in this graph<http://rgm2.lab.nig.ac.jp/RGM_results/psych:omega.graph/omega.graph_002_big.png>,
>  and
> alpha uses average inter-item correlations.
>
> 1. What I don't understand is, in what condition, omega reliability
> coefficient would be higher than alpha coefficient,  and vice versa?
>
> 2. Can I assume if the correlations between the subfactors and the
> variables are higher, the omega coefficient would also be higher  (as shown
> in the omega graph<http://rgm2.lab.nig.ac.jp/RGM_results/psych:omega.graph/omega.graph_002_big.png>
> )?
>
> Any advice is appreciated!
>
> Thanks.
>
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>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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