Hello,

I am trying to determine LD50 and LD95 using dose.p in MASS however some of the Residual variance is larger than the degrees of freedom. Please can anyone help with any advice as to how i can correct for this?

Here is the model as inputted into R



y<-cbind(dead,n-dead)

model<-glm(y~log(conc),binomial)
summary(model)

xv<-seq(min(log(conc)-1),max(log(conc)+1),0.01)
lines(xv,predict(model,list(conc=exp(xv)),type="response"))

dose.p(model,p=c(0.10,0.25,0.5,0.75,0.90,0.95))



Thanks

Adaku



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