R help - Jan 2012 - ED50 calculation in drc package

Hi,

I am trying to use drc package to calculate IC50 value. The ED50 calculated in
some models (LL4 for example) as a response half-way between the upper and lower
limit, which is the definition of the relative IC50 value. Does that mean the
ED50 in drc package is IC50? How the ED function in drc package distinguish to
estimate ED or IC values?

Thanks a lot


	[[alternative HTML version deleted]]

Lixia:

This is not fundamentally an R issue. You seem to have some confusion
about what IC50's and ED50's are in the statistical modeling context.
I suggest you consult one of the fine statisticians at MD Anderson to
help you resolve your confusion.

Cheers,
Bert

On Tue, Jan 3, 2012 at 10:11 AM, Diao,Lixia <ldiao at mdanderson.org>
wrote:
> Hi,
>
> I am trying to use drc package to calculate IC50 value. The ED50 calculated
in some models (LL4 for example) as a response half-way between the upper and
lower limit, which is the definition of the relative IC50 value. Does that mean
the ED50 in drc package is IC50? How the ED function in drc package distinguish
to estimate ED or IC values?
>
> Thanks a lot
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
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http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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Phone: 467-7374
Website:
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