[Rasch] Reliability in Facets

Mike Linacre rmt at rasch.org
Thu Feb 2 12:57:27 EST 2012

Thank you for your question, Stuart.

The two kinds of reliability appear to be "Spearman Reliability" and 
"Cronbach Generalizability".

My understanding is that:
Spearman Reliability is internal to the samples in the current dataset
Cronbach Generalizability attempts to extrapolate reliability to the 
populations those samples represent.

Mike L.

At 2/1/2012, you wrote:
>Hello fellow Raschies, I'm confused about the notion of reliability in a 
>facets analysis where teacher ratings are moderated by observers. As I see 
>it, there are two ways to conceptualize reliability: 1) true variation 
>among teachers / (true variation among teachers + measurement error) 2) 
>true variation among teachers / (variation among teachers + variation 
>among raters (severity) + variation among other facets + residual 
>variation) (For the latter, I used the measure S.D. from the Facets output 
>squared for each source of variance, plus the variance of the residuals 
>from the residual file.) In the work I'm doing analyzing teacher ratings 
>data using the Danielson Framework for Teaching, reliability 1) is .93, 
>but reliability 2) is .35. How do I reconcile these two? Are they two 
>different kinds of reliability?

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