# 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
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## Re: Query : Chi Square goodness of fit test

 > chisq.test(counts, p=Expected/sum(Expected), simulate.p.value =FALSE, correct = FALSE)          Chi-squared test for given probabilities data:  counts X-squared = 40.5207, df = 13, p-value = 0.0001139 Warning message: l'approximation du Chi-2 est peut-être incorrecte in: chisq.test(counts, p = Expected/sum(Expected), simulate.p.value = FALSE, but the use of Chi2 test is incorrect since some of Expected frequencies are lower than 5. ------------------------------------------------------------------- Jacques VESLOT CNRS UMR 8090 I.B.L (2ème étage) 1 rue du Professeur Calmette B.P. 245 59019 Lille Cedex Tel : 33 (0)3.20.87.10.44 Fax : 33 (0)3.20.87.10.31 http://www-good.ibl.fr------------------------------------------------------------------- priti desai a écrit : > 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-help> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html> ______________________________________________ [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