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st: RE: Calculating weighted kappa for multiple raters


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Calculating weighted kappa for multiple raters
Date   Thu, 3 Dec 2009 18:59:02 +0100

<>

"  (i have attached my full code in a do-file)"


You have, and it is unlikely to go down well with the community...
See the FAQ!

HTH
Martin

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Karen Wright
Sent: Donnerstag, 3. Dezember 2009 17:46
To: statalist@hsphsun2.harvard.edu
Subject: st: Calculating weighted kappa for multiple raters

Dear list,

I have a problem that is perhaps more to do withprogramming than anything
else.  i am not experieced in programming stata and so have given up writing
an ado-file program for whta I am trying to do, but unfortunately I am stil
encountering problems!

  I am trying to calculate weighted kappa for multiple raters, i have
attached a small word document with the equation.  My problem occurs when I
am trying to calculate marginal totals.  I am trying to create a total of
the frequency for each rater, within each category and multiply these
together, as shown in the equation.

The current method i am employing to do this is :


forval a=1/`r' {
	summ _freq if reader1==`a' 
	loc A_`a' = r(sum)
	summ _freq if reader2==`a' 
	loc B_`a' = r(sum)
	summ _freq if reader3==`a' 
	loc C_`a' = r(sum)
}
forval a=1/4 {
	forval b=1/4 {
		forval c=1/4 {
gen d_`a'`b'`c' = weight*`A_`a''*`B_`b''*`C_`c'' if reader1==`a' &
reader2==`b' & reader3==`c'
		}
	}
}
egen den = rowtotal(d_111-d_`r'`r'`r')
drop d_*
summ(den)
loc denom = r(sum)
di `denom'


  (i have attached my full code in a do-file)

But this becomes very lengthy and produces too many variables to do for any
sufficient amount of raters.  Eventually i hope to analyse gradings from
>100 raters, and yet with my current methods stata cannot compute it for
only 8!  too many variables created.

Is there another way anyone with much better stata programming experience
than me can see to proceed?

Thank you, any help is much appreciated!
Karen




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