Why is 95% CI for ICC so large?

Posted by J McClure on Mar 10, 2011; 4:50am
URL: http://spssx-discussion.165.s1.nabble.com/Why-is-95-CI-for-ICC-so-large-tp3422764.html

Hi,
I have run ICC's with a 95% CI to compare agreement self reported rating
by the patient and the doctor's rating by another characteristic. For
example, I divided the sample between the patient's who had major
depression and those without major depression and determined the
agreement of the MD's with patients with major depression and separately
agreement with patient's without major depression.
The ICC for those without depression (n=153) was 0.43 (95%CI 0.23, 0.52
) and for those with depression (n=224) it was 0.43 (CI 0.04, 0.66).
Why is the CI for the second group so much wider than for the first? The
ICC syntax I am using is   /ICC=model (random) type(absolute).
Thanks for any help,
Jan

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