Re: [R] Under-dispersion - a stats question?

2005-10-12 Thread Martin Henry H. Stevens
Hello all: Thank you for you interest. This text of this email is in the attached R-help.r file. The R script is in R-helpscript.r. The data set is wk6trial.csv. One of my students has performed a laboratory experiment with petri dishes containing hundreds of species of bacteria, and six

Re: [R] Under-dispersion - a stats question?

2005-10-11 Thread Kjetil Holuerson
Martin Henry H. Stevens wrote: Hello all: I frequently have glm models in which the residual variance is much lower than the residual degrees of freedom (e.g. Res.Dev=30.5, Res.DF = 82). Is it appropriate for me to use a quasipoisson error distribution and test it with an F

Re: [R] Under-dispersion - a stats question?

2005-10-11 Thread Prof Brian Ripley
On Mon, 10 Oct 2005, Martin Henry H. Stevens wrote: Hello all: I frequently have glm models in which the residual variance is much lower than the residual degrees of freedom (e.g. Res.Dev=30.5, Res.DF = 82). Is it appropriate for me to use a quasipoisson error distribution and test it with

Re: [R] Under-dispersion - a stats question?

2005-10-11 Thread Jari Oksanen
On Tue, 2005-10-11 at 17:16 -0400, Kjetil Holuerson wrote: Martin Henry H. Stevens wrote: Hello all: I frequently have glm models in which the residual variance is much lower than the residual degrees of freedom (e.g. Res.Dev=30.5, Res.DF = 82). Is it appropriate for me to use a

[R] Under-dispersion - a stats question?

2005-10-10 Thread Martin Henry H. Stevens
Hello all: I frequently have glm models in which the residual variance is much lower than the residual degrees of freedom (e.g. Res.Dev=30.5, Res.DF = 82). Is it appropriate for me to use a quasipoisson error distribution and test it with an F distribution? It seems to me that I could

Re: [R] Under-dispersion - a stats question?

2005-10-10 Thread Peter Dalgaard
Martin Henry H. Stevens [EMAIL PROTECTED] writes: Hello all: I frequently have glm models in which the residual variance is much lower than the residual degrees of freedom (e.g. Res.Dev=30.5, Res.DF = 82). Is it appropriate for me to use a quasipoisson error distribution and test it