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Re: st: clogit data format
We did the kappa analysis on the data before we dichotomized it and then
used Stata's "kap" to compare pairs using a bootstrapped sample so the N
isn't comparable.
Margaret
Cathy L. Antonakos wrote:
With a kappa analysis, which Margaret wrote she had done, wouldn't the
kappa also be undefined in the case of no variance between raters?
I've just run across this issue in an analysis of multiple raters. It
seems the kappa analysis should also have failed for other than the
290 cases with variance, so the N for the clogit would not have been a
surprise. Cathy ---
Subject: Re: st: clogit data format
Thanks, Nick!
I was asked to do a clogit but will summarize as you suggested and see
where that leads.
Margaret
Nick Cox wrote:
If I understand this correctly, individuals for whom all raters agree
cannot be included in a -clogit- analysis. That seems to rule it out
absolutely
as a way of examining the structure of agreement and disagreement.
There are many ways to look at the data, depending on what data
generation process
you have in mind. It's not clear to me that a binary response
inescapably implies a logit analysis. Missings aside, four
ratings
for each individual imply that your data can be collapsed with loss
of information to a table of the frequencies of 16 joint outcomes:
0000
0001
0010
0011
...
1111
which may allow structure to be discerned. Here "0000" means all four
raters
assign "0", and so forth.
Nick
[email protected]
Margaret R Grove
To clarify further where I think the problem may lie:
PHREG output notes "Number of Observations Read 2300" and "Number
of Observations Used 2000" (300 have missing values for the
dependent variable)
CLOGIT notes that 1710 observations (496 groups) were dropped because of
all negative or all positive outcomes and our final number of
observations is 290!
With this I wonder if comparing the two methods makes sense and which
method (PHREG or CLOGIT) is preferable (if any)?
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