From charlie@stat.umn.edu  Sun Oct 29 15:29:58 2000
From: charlie@stat.umn.edu (charlie@stat.umn.edu)
Date: Sun, 29 Oct 2000 16:29:58 +0100 (MET)
Subject: [Rd] prop.test and x = 0 (PR#714)
Message-ID: <200010291529.QAA23204@pubhealth.ku.dk>

Full_Name: Charles J. Geyer
Version: 1.1.1
OS: linux-gnu
Submission from: (NULL) (134.84.86.22)


prop.test(0, 30)

95 percent confidence interval:
 0.003043053 0.141320480 

Clearly absurd.  You need theory to be this stupid. :-)

I suggest adding

if (p.c >= 1) p.u <- 1

just after line 59 of the current version of prop.test and

if (p.c <= 0) p.l <- 0

just after line 62 of the current version of prop.test.

With these patches, prop.test produces conservative confidence intervals
for all p and n = 30.  The current version fails catastrophically for 0 < p <
.003
where of course it has actual coverage probability zero.

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[Rd] prop.test and x = 0 (PR#714)
charlie@stat.umn.edu