I have plotted the effects of a model glm( A ~ B, family=poisson, data=data) both with the sjplot R package and with the effects package. However, my A variable is a percentage (min=0, max=100) and the effect plot shows A values higher than 100. What should I do?
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1 Answer
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If the prediction limits or confidence intervals exceed some limit beyond which predictions/inference become unphysical, then your model is misspecified.
The most straightforward example of this is using linear regression to perform prediction of a continuous covariate's affect on a binary outcome. Eventually, the model will predict something above/below 1/0.
The poisson's mean is supported on the positive reals, and so if your outcome is bounded to the unit interval, you may consider a logistic regression or a beta regression. To say more, we would need to know what you are modelling and perhaps see some data.
answered Jul 22, 2019 at 14:10
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$\begingroup$ thank you so much to @mkt and DemetriPananos $\endgroup$– SaraCommented Jul 25, 2019 at 9:14
Ais a percentage. In that case, I'd recommend using logistic regression or beta regression. $\endgroup$