Date: Thu, 14 Sep 2000 14:03:22 -0400
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
Subject: Re: Why offset in confidence interval for proportions?
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You are talking about the Joint Commission on the Accreditation of Healthcare
Most Joint Commission events reporting that I've heard of (keep in mind that I
have only heard of
a *small part* of what they do) are for *rare* events--adverse outcomes,
sentinel events, deaths etc.
These events would not be distributed Gaussian or even Z, but they would have
some skewed distribution.
I think that accounts for the off-centering of the 99% CI. More than that, I am
not sure about the exact
formula. Recommend you ask someone with a PhD.
z <gzuckier@MY-DEJA.COM> on 09/14/2000 11:37:26 AM
Please respond to z <gzuckier@MY-DEJA.COM>
cc: (bcc: Mark K Moran/CSD/HQ/BOC)
Subject: Why offset in confidence interval for proportions?
Hi. This is more a stats question than a SAS one, but.... I'm trying to
wade through the JCAHO ORYX reporting requirements. Their formulae for
upper and lower limits for a 99% confidence interval for a proportion
n=Number of patients
I can't exactly see where this comes from (I would have come up with
p(+or-)Z(p(1-p)/n)^.5 myself), and more to the point, this gives me a
confidence interval whose center is offset from p by the (Z^2)/2n term.
Waiting for the JCAHO to clarify is a slow process, in the meantime,
can anyone explain the theory behind this calculation? Thanks.
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