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st: Random effect Kappa?


From   Eduardo Nunez <enunezb@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Random effect Kappa?
Date   Sat, 6 Feb 2010 21:47:48 -0500

Dear Statalisters:

I am seeking your guidance on how to perform either random effect or
accounting for autocorrelation when estimating kappa statistics. I
need to figure out a way to perform this statistical analysis in
Stata. If not possible, I would appreciate any other software capable
of it.

These are the details and challenge I have before me:
1. 7 blinded scorers (dermatologists, plastic surgeon)
2. 188 photographs representing four facial compartments
3. 10 possible scores (0-9, none to severe laxity) for each photo by
each blinded scorer

The data for the first scorer looks like:
Scorer1
pte_id    photo_id    laxity_score(0-9)    facial_region(1-4)
lead_author_score
1    1    8    3    7
1    25   3    1    3
2    4    0    4    0
and so on....

For the rest of the scorer (2 to 7), I have similar data structure.

Outcomes:
1) Agreement (kappa) of each scorer with the lead author score (to
compare each of the blinded scorer's results against an "answer key"
provided by the lead author).
2) Agreement (kappa) for the comparison between each scorer (1 vs 2, 1
vs 3, 2 vs 1, etc).
2) A summary kappa integrating each kappa from 1),
3) A summary kappa integrating each kappa from 2),

Questions:
1) Because one patient can contributes to several photos and to
different facial regions, I assume measures from the same pte are
likely to be correlated. How should I adjust for that? random effect?
2) Which is the best way to pool individual kappas into a grand summary kappa?

Any advice would be very much appreciated.


Eduardo Nunez, MD, MPH
Valencia, Spain
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