Dear R users, I am trying to reproduce table 7.4.12 (page 131) from Snedechor & Cochran (eigth edition); the example is counts of weed seeds with a fitted Poisson distribution, tested for goodness-of-fit using a Chi-square:
observed=c(3,17,26,16,18,9,3,5,0,1,0,0) expected=dpois(0:11,lambda=3.020408)*98 chisq.test(observed,p=expected,rescale.p=T) Now the problem I have is that chisq.test gives me the chi-squared value of roughly 8.30 (which is the value given by Snedechor & Cochran), but I am wondering why the warning message occurs at the end of the test. Further, it is not clear to me how these calculations could be done using the full dataset of N=98 observations: observed.full=rep(0:11,c(3,17,26,16,18,9,3,5,0,1,0,0)) What would the correct specification for a chisq.test against a poisson distribution look like in this case? Thanks for your help! Best wishes Christoph ## Chi-squared test for given probabilities data: observed X-squared = 8.2628, df = 8, p-value = 0.4082 Warning message: Chi-squared approximation may be incorrect in: chisq.test(observed, p = expected, rescale.p = T)
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