Andreas,
My suggestion:
If you want to compare your simulations with actual observations then
you should include residual error in the simulation. The observations
will include noise as well as the 'true' value so in order to compare
observations with simulated observations you need the residual error.
If you want to use the simulation to describe the 'true' value then dont
include the residual error. Residual error is assumed to have a mean of
zero around the 'true' value so there is no point in adding this kind of
noise if you are trying to predict the 'true' value.
Your examples suggest to me that you are trying to predict the 'true'
value -- not trying to match simulations directly with measured values.
If my guess is correct then you dont need to include residual error.
However, if you are using simulations for some kind of predictive check
(visual, numerical, statistical) that will be compared to distribution
statistics of the observations then you should include residual error.
Nick
andreas lindauer wrote:
Dear NMUSERS,
The recent discussion about simulation with a nonparametric method
brought a general question concerning monte-carlo simulations into my
mind. When should simulations be performed with residual error and
when not. I am especially interested in comments regarding the
following scenarios when the result of the simulation should be
reported as mean or median and 90% prediction interval:
1. Simulated response at a particular time point (eg. Trough values)
2. Simulated response at a particular time point (x) relative to
baseline response (IPRED(t=x)/IPRED(t=0) vs. DV(t=x)/DV(t=0) )
3. Simulated time of maximal response (eg. Tmax)
Thanks and best regards, Andreas.
____________________________
Andreas Lindauer
Department of Clinical Pharmacy
Institute of Pharmacy
University of Bonn
An der Immenburg 4
D-53121 Bonn
phone: + 49 228 73 5781
fax: + 49 228 73 9757
--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand
n.holf...@auckland.ac.nz tel:+64(9)923-6730 fax:+64(9)373-7090
mobile: +33 64 271-6369 (Apr 6-Jul 20 2009)
http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford
