# Query : Chi Square goodness of fit test

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## Query : Chi Square goodness of fit test

 I want to calculate chi square test of goodness of fit to test, Sample coming from Poisson distribution. please copy this script in R & run the script The R script is as follows ########################## start ######################################### No_of_Frouds<- 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) N <- length(No_of_Frouds) # Estimation of Parameter lambda<- sum(No_of_Frouds)/N lambda pmf  <- dpois(i, lambda, log = FALSE) step_function  <- ppois(i, lambda, lower.tail = TRUE, log.p = FALSE) # Chi-Squared Goodness of Fit Test # Ho: The data follow a Poisson distribution Vs H1: Not Ho Frauds <- c(1:13) counts<-  c(2,3,3,5,7,2,1,1,2,3,2,1,1,0)  # Observed frequency Expected <-c(0.251005528,1.224602726,2.987288468,4.85811559,5.925428863,5.7817821 03,4.701348074,3.276697142,1.998288788,1.083247457,0.528493456,0.2344006 79,0.095299266,0.035764993) chisq.test(counts, Expected, simulate.p.value =FALSE, correct = FALSE) ######################### end ######################################## The result of R is as follows   Pearson's Chi-squared test data:  counts and poisson_fit X-squared = 70, df = 65, p-value = 0.3135 Warning message: Chi-squared approximation may be incorrect in: chisq.test(counts, poisson_fit, simulate.p.value = FALSE, correct = FALSE) 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 calculations in R. ######################################################################## ###################### Awaiting your positive reply. Regards. Priti. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide! http://www.R-project.org/posting-guide.html