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st: a bug in the new command kapci?


From   Jose Maria Pacheco de Souza <jmpsouza@usp.br>
To   statalist@hsphsun2.harvard.edu
Subject   st: a bug in the new command kapci?
Date   Fri, 01 Oct 2004 19:39:30 -0300

Dear David and Statalisters:

The new commands of confidence interval for kappa is welcome.
But it seems to have a bug. I compared the results on page 1519 of the article (kappa=.81, ci= .67-.92, and ci= .70-.92) executing the commands

. kap var1 var2

Expected
Agreement Agreement Kappa Std. Err. Z Prob>Z
-----------------------------------------------------------------
90.68% 51.29% 0.8086 0.0920 8.79 0.0000

. kapci var1 var2

Expected Observed -- Binomial Exact --
Agreement Agreement [95% Conf. Interval]
--------------------------------------------
51.29% 90.68% 83.93% 95.25%

Kappa [95% Conf. Interval] Z Prob>Z
-------------------------------------------------
0.8086 0.3400 0.8914 8.79 0.0000

Clearly the result 0.3400 for the lower limit is not correct.

In the ado file for kapci it is missing -(1/3)*`y2' in the equation for -lb-; adding it, I got the correct result:

kapci var1 var2

Expected Observed -- Binomial Exact --
Agreement Agreement [95% Conf. Interval]
--------------------------------------------
51.29% 90.68% 83.93% 95.25%

Kappa [95% Conf. Interval] Z Prob>Z
-------------------------------------------------
0.8086 0.6735 0.8914 8.79 0.0000

I did not checked the .ado for kappaci.
Greetings,
Jose Maria


--
Jose Maria Pacheco de Souza, Professor Titular
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904 - S. Paulo/SP - Brasil
fones (11)3082-3886; (11)3066-7724; (11)3768-8612; (11)3714-2403
fax (11)3082-2920; (11)3714-2403
www.fsp.usp.br/~jmpsouza
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