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st: Kappci problem


From   "Nigel Armfield" <[email protected]>
To   <[email protected]>
Subject   st: Kappci problem
Date   Thu, 21 Jun 2007 21:29:18 +1000

Hi,

I am trying to an analysis of agreement between two raters (dichotomous
variables) using kappci.
Each set of data is 14 pairs of Y/N.

I'm confused by the behaviour of kappci - sometimes it produces a result
that looks fine, sometimes it produces a result but the kappa value
seems way too low. Other times it fails with an odd error message.

Here's an example of the error:

var1	var2	var3
1	y	y
2	y	y
3	n	y
4	y	y
5	y	y
6	y	y
7	y	y
8	y	y
9	y	y
10	n	y
11	y	y
12	y	y
13	y	y
14	y	y

. kappci var2 var3, pos("y")
'.' found where number expected
r(7);

I have re-entered the data manually but with no luck.

With a different set of data:

var1	var2	var3
1	y	y
2	n	y
3	y	y
4	y	y
5	y	y
6	y	y
7	y	y
8	y	y
9	y	y
10	y	y
11	y	y
12	.	.
13	y	y
14	y	y

. kappci var2 var3,pos("y")

 Expected    Observed   -- Binomial Exact --
Agreement   Agreement   [95% Conf. Interval]
--------------------------------------------
   80.61%      92.86%      66.13%     99.82%

  Kappa  [95% Conf. Interval]        Z     Prob>Z
-------------------------------------------------
 0.6316     0.0418     0.9325     2.54     0.0055

Any ideas would be gratefully received - I've been going round in
circles and getting nowhere fast for the last few hours.

Thanks in advance,

Nigel

--

Nigel R. Armfield. MSc, MIEEE, MIET.
Senior Research Assistant (Telepaediatrics)
Centre for Online Health
The University of Queensland
Level 3, Royal Children's Hospital
Herston 4029
Australia

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