[Rasch] Fwd: Reliability, separation and strata

Mike Linacre mike at winsteps.com
Wed Mar 1 20:15:45 AEDT 2017


G and H are described at http://www.rasch.org/rmt/rmt94n.htm and 
http://www.rasch.org/rmt/rmt163f.htm - they both depend on the sample of 
persons, and expect the sample to have a normal distribution.

Ben Wright's method at http://www.rasch.org/rmt/rmt144k.htm is 
independent of the sample of persons. It is not G or H.
Ben Wright suggests that if you need G or H for a skewed sample, then 
resample a normal distribution of persons from the skewed sample. See 
"Later Note" at the bottom of http://www.rasch.org/rmt/rmt144k.htm


Mike L.

On 3/1/2017 6:07 PM, Fabio La Porta wrote:
> Hello Mike,
> I understand that 1) is the formula for the separation ratio (G), but 
> I do not understand the formulas for 2) and 3).
> Are these related to the calculation of the reliability index starting 
> from H [(4G+1)/3 ?] and, respectively, the method suggested by Ben 
> Wright for skewed distributions in http://www.rasch.org/rmt/rmt144k.htm?
> Also, the above method for skewed distributions allows to calculate G 
> or H?

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