R help - Feb 2001 - logistic regression with percentages

Hello

I've got some data and I want to fit a binomial glm. The problem is that I
don't have the number of successes or failures, I have only the percentages.
If I want to make all these numbers integers, I have to multiply them for 1000,
because there are some low percentages (0.05%). Besides, I don't know if
this is correct.
Any help?

Thanks in advance, and sorry for my english

Julio G?mez
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"Oscar" <orp at intras.es> writes:

> Hello
> 
> I've got some data and I want to fit a binomial glm. The problem is
that > I don't have the number of successes or failures, I have only the
> percentages. If I want to make all these numbers integers, I have to >
multiply them for 1000, because there are some low percentages (0.05%). >
Besides, I don't know if this is correct.
> Any help?
> 
> Thanks in advance, and sorry for my english
> 
> Julio G=F3mez
If you really only have percentages, then your analysis will come out
wrong whatever you do: It makes a substantial difference whether 50%
means "1 of 2" or "316 of 632"!

If you can get the total number in each group, you should *divide* the
percentages by 100 to get probabilities and use the weight= argument
to glm with the number of cases.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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