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st: RE: reliability with ordinal data-Kendall's w?
From
Nick Cox <[email protected]>
To
"'[email protected]'" <[email protected]>
Subject
st: RE: reliability with ordinal data-Kendall's w?
Date
Mon, 13 Dec 2010 20:12:47 +0000
It seems to me that Somers' [NB] d is very well supported in Stata given Roger Newson's routines.
I can't see much point to plots of the form re-invented by Bland and Altman in this case. Nor does the limits of agreement approach transfer other than queasily to a 4-point graded scale. -tabplot- from SSC offers one of various graphical alternatives. Diagonal agreement and off-diagonal disagreement will be pretty clear.
Nick
[email protected]
Ploutz-Snyder, Robert (JSC-SK)[USRA]
I need to perform a reliability analysis among two raters who rated the same observations independently. Observations are rated on an ordinal scale, taking 4 distinct values in increasing order. Neither rater is assumed the "gold standard." There are a LOT of ties in my dataset (a good thing in terms of rater reliability).
I came across some web hits about Kendall's W, which is different from the more familiar tau. Can anyone attest to whether this is the best way to go about a reliability analysis with ordinal data? Is there a way to implement on Stata?? How does W differ from tau, and Somer's d??
Are there other/better methods that I should be considering too?
Also--for those knowledgeable about reliability analyses... I think that eventually I would like to graph these data with something akin to the Bland-Altman plots. Do you take issue with that approach given that the data are not continuous? Are the BA Limits of Agreement valid in this situation??
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