Hello all,
I'm running very simple regression but face a problem of non-homogeneity of
variance, but with a decreasing variance with increasing mean...I do not
know how to deal with that.
this relationship doesn't seem to be strong, but it's my first time to see
something like that, and would like to know what to do if one day it becomes
stronger. I tested just for fun some transformation but was not able to get
a better model. I do not know if it can help, but my predictor variable is a
kind of gamma poisson-shaped-like zero-rich distribution (continuous of
course), highly overdispersed.
If one know how to deal with decreasing variance, I would appreciate any
advice (I tried to modelize negative variance-mean relationship in a new
quasi- family this was prohibited, only constant, mu, mu^x (and mu(1-mu) for
binomial) were allowed). I've definitively reached the border of the
statistical black box for me.
thanks
simon
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