Hello! I'm doing logistic regression analysis for occurrence of a fungal disease of oat in four soil treatments, with four replicates. I use the proc GENMOD. Four soil treatments are "no till", "spring cultivation", "fall cultivation" and "till". Fgram is the independent variable, the occurrence of fungal disaese out of 100 samples. Total sample size per plot is 100 grains of yield. For some reason the replicate's degrees of freedom equals to zero and I get no results from them. I have similar other datasets and the analysis goes just fine. What could be the problem? Can I still use the probabilities from the treatments? My dataset: treatment plot replicate fgram Ntot till 101 2 14 100 fall cult 102 4 19 100 no till 103 1 5 100 spring cult 104 3 8 100 fall cult 201 4 13 100 till 202 2 6 100 spring cult 203 3 9 100 no till 204 1 9 100 spring cult 301 3 8 100 no till 302 1 6 100 till 303 2 15 100 fall cult 304 4 8 100 spring cult 401 3 2 100 no till 402 1 10 100 till 403 2 8 100 fall cult 404 4 8 100 My code: proc GENMOD data=WORK.tillageyield;
Title "Logistic regression analysis for f.graminearum occurrrence in yield, treatments are compared to till";
Class treatment (ref="till") replicate/param=ref;
model fgram/Ntot = treatment replicate/
dist=binomial
link=logit
waldci;
run;
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