From constant at unb.br  Sun Nov 16 01:00:09 2008
From: constant at unb.br (constant at unb.br)
Date: Sun, 16 Nov 2008 01:00:09 +0100 (CET)
Subject: [Rd] chisq.test with simulate.p.value=TRUE (PR#13292)
Message-ID: <20081116000009.8029A2834615@mail.pubhealth.ku.dk>

Full_Name: Reginaldo Constantino
Version: 2.8.0
OS: Ubuntu Hardy (32 bit, kernel 2.6.24)
Submission from: (NULL) (189.61.88.2)


For many tables, chisq.test with simulate.p.value=TRUE gives a p value that is
obviously incorrect and inversely proportional to the number of replicates:

> data(HairEyeColor)
> x <- margin.table(HairEyeColor, c(1, 2))
> chisq.test(x,simulate.p.value=TRUE,B=2000)
        Pearson's Chi-squared test with simulated p-value (based on 2000
        replicates)
data:  x
X-squared = 138.2898, df = NA, p-value = 0.0004998

> chisq.test(x,simulate.p.value=TRUE,B=10000)
X-squared = 138.2898, df = NA, p-value = 1e-04

> chisq.test(x,simulate.p.value=TRUE,B=100000)
X-squared = 138.2898, df = NA, p-value = 1e-05

> chisq.test(x,simulate.p.value=TRUE,B=1000000)
X-squared = 138.2898, df = NA, p-value = 1e-06
...

Also tested the same R version under Windows XP and got the same results.



[Rd] chisq.test with simulate.p.value=TRUE (PR#13292)
constant at unb.br