Re: [R] exact 95% confidence intervals

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Wed 27 Sep 2006 - 13:11:11 GMT

Frank E Harrell Jr <f.harrell@vanderbilt.edu> writes:

> Peter Dalgaard wrote:
> > "XinMeng" <xmeng@capitalbio.com> writes:
> >
> >> Hello sir:
> >
> >> As to the 2*2 table format for reporting results comparing a new
> >> test to true diagnosis,when I got the sensitivity and
> >> specificity,how can I calculate the exact 95% confidence intervals
> >> (based on the binomial distribution) for sensitivity and specificity
> >> via R?
> > Just run binom.test on the data from each column (or row, depending
> > on
> > which way you turn the tables).
> >
>
> But beware of exact binomial intervals - they are often not very
> accurate. Wilson and other intervals are generally better. For
> example see the binconf function in the Hmisc package.

I suppose that by "accurate" you mean that they are generally better at getting the coverage rate right?

The "exact" intervals are strictly conservative, but at least predictably so. The whole thing is largely a matter of taste to my mind, but I know that other people (notably Alan Agresti) have stronger opinions.

(People taking an interest in this may want to have a look at http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval )

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Wed Sep 27 23:23:53 2006

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