[R] Left censored responses in mixed effects models

[Don MacQueen]

I assume you've looked at the NADA package(?) While I don't believe 
it goes as far as dealing the mixed effects models, it might give you 
a starting point, and possibly some additional references.

-Don

At 9:08 AM -0700 5/12/08, Bert Gunter wrote:
>Dear R Fellow-Travellers:
>
>What is your recommended way of dealing with a left-censored response
>(non-detects) in (linear Gaussian) mixed effects models?
>
>Specifics: Response is a numeric positive measurement (of volume, actually);
>but when it falls below some unknown and slightly random value (depending on
>how the sample is prepared and measured), it cannot be measured and is
>recorded as 0.
>
>There is some statistical literature on this, but I was unable to find
>anything that appeared to me to implement a strategy in any R package. If it
>matters, I am less interested in inference than in removing possible bias in
>estimation.
>
>Feel free to respond off-list if you feel that this would not be of general
>interest.
>
>Cheers,
>
>Bert Gunter
>Genentech
>
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-- 
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
925-423-1062