[R] Chi-square test

[David L Carlson]

And probably why chisq.test has the rescale.p= argument. Your second problem with small expected values can be handled with simulate.p.value=.

> chisq.test(f, p=p11)
Error in chisq.test(f, p = p11) : probabilities must sum to 1.
> 1-sum(p11)
[1] 4.3036e-08
> chisq.test(f, p=p11, rescale.p=TRUE)

        Chi-squared test for given probabilities

data:  f
X-squared = 7.6268, df = 14, p-value = 0.9078

Warning message:
In chisq.test(f, p = p11, rescale.p = TRUE) :
  Chi-squared approximation may be incorrect
> chisq.test(f, p=p11, rescale.p=TRUE, simulate.p.value=TRUE)

        Chi-squared test for given probabilities with simulated p-value (based
        on 2000 replicates)

data:  f
X-squared = 7.6268, df = NA, p-value = 0.7996

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Berend Hasselman
Sent: Friday, February 20, 2015 12:13 PM
To: pari hesabi
Cc: r-help at r-project.org
Subject: Re: [R] Chi-square test


> On 20-02-2015, at 19:05, pari hesabi <statistics84 at hotmail.com> wrote:
> 
> Hello,
> If the vector of observed frequencies is:  f<-c(0,0,0,2,3,6,17,15,21,21,14,10,5,1,5)
> and the vector of probability :p11<-c(7.577864e-06, 1.999541e-04  ,1.833510e-03,  9.059845e-03, 2.886977e-02, 6.546229e-02 ,1.124083e-01, 1.525880e-01, 1.689712e-01, 1.563522e-01,   1.232031e-01, 8.395000e-02, 5.009534e-02, 2.645857e-02,0.0205403)
> The sum of the probabilities is equal to one. But when I want to do the the Chi-square test, I get this error: probabilities must sum to one.

print  sum(p11)-1

> Does anybody know the reason?

R FAQ 7.31  (http://cran.r-project.org/doc/FAQ/R-FAQ.html)

Berend

> Best Regards,
> pari
> 		 	   		  
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