[R] Query:chi-squre test

From: priti desai <priti.desai_at_kalyptorisk.com>
Date: Mon 10 Jul 2006 - 23:44:43 EST


Hi,
  I have calculated chi-square goodness of fit test,Sample coming from Poisson distribution.
please copy this script in R & run the script The R script is as follows

########################## start
#########################################

No_of_Frauds<-
c(4,1,6,9,9,10,2,4,8,2,3,0,1,2,3,1,3,4,5,4,4,4,9,5,4,3,11,8,12,3,10,0,7)

lambda<- mean(No_of_Frauds)  

# Chi-Squared Goodness of Fit Test

# Ho: The data follow a specified distribution Vs H1: Not Ho

# observed frequencies

variable.cnts <- table(No_of_Frauds)
variable.cnts

variable.cnts.prs <- dpois(as.numeric(names(variable.cnts)), lambda) variable.cnts.prs

variable.cnts <- c(variable.cnts, 0) 
variable.cnts
variable.cnts.prs <- c(variable.cnts.prs, 1-sum(variable.cnts.prs))
variable.cnts.prs

tst <- chisq.test(variable.cnts, p=variable.cnts.prs) Tst

######################### end ########################################


The result of R is as follows

Warning message:
Chi-squared approximation may be incorrect in: chisq.test(variable.cnts, p = variable.cnts.prs)
> tst

        Chi-squared test for given probabilities

data: variable.cnts
X-squared = 40.5614, df = 13, p-value = 0.0001122

But I have done calculations in Excel. I am getting different answer.

Observed = 2,3,3,5,7,2,1,1,2,3,2,1,1,0
Expected=0.251005528,1.224602726,2.987288468,4.85811559,5.925428863,5.78 1782103,4.701348074,3.276697142,1.998288788,1.083247457,0.528493456,0.23 4400679,0.095299266,0.035764993

 Estimated Parameter =4.878788

Chi square stat = 0.000113

My excel answer tally with the book which I have refer for excel. Please tell me the correct calculation in R. And how to interprit the results in R.

Thanks.
Regards.
Priti.



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Jul 10 23:52:53 2006

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.1.8, at Tue 11 Jul 2006 - 02:15:37 EST.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.