Re: [NMusers] Minimum patients number...

Greetings -

You have twice the data (total observations), but only the same amount of
information (independent observations), and it is the latter which drives t=
he
precision/accuracy of the estimation procedure, adjusting downwards if the=
 
total number of observations goes up (adjusting upwards with the correlatio=
n
of the additional observations, i.e. multiple measurements of "pretty much=
 
the same thing").

best,
-tony

blindglobe_at_gmail.com
Muttenz, Switzerland.
"Commit early,commit often, and commit in a repository from which we can
easily roll-back your mistakes" (AJR, 4Jan05).

On Saturday 27 January 2007 20:49, Mark Sale - Next Level Solutions wrote:
> Mats,
> The "rules of thumb" are indeed empiric observations from one
> variable. But, if you have two dependent variables, you have twice the
> data (one time point, two DVs), and twice the parameters. So, I think
> the rule may be consistent, but I don't know how valuable it is in the
> first place.
>
>
>
> Mark Sale MD
> Next Level Solutions, LLC
> www.NextLevelSolns.com
>
> > -------- Original Message --------
> > Subject: RE: [NMusers] Minimum patients number...
> > From: "Mats Karlsson" <mats.karlsson_at_farmbio.uu.se>
> > Date: Sat, January 27, 2007 11:41 am
> > To: "'Ahmed Hawwa'" <ahawwa1_at_yahoo.com>, <nmusers_at_globomaxnm.com>
> >
> > Hi,
> >
> > I think that all the rules of thumb that have been mentioned are based =
on
> > the assumption that you have a single observed variable. If you observe
> > several, you certainly can expect to estimate more parameterers.
> >
> > Mvh,
> > Mats
> >
> >
> > Mats Karlsson, PhD
> > Professor of Pharmacometrics
> > Div. of Pharmacokinetics and Drug Therapy
> > Dept. of Pharmaceutical Biosciences
> > Faculty of Pharmacy
> > Uppsala University
> > Box 591
> > SE-751 24 Uppsala
> > Sweden
> > phone +46 18 471 4105
> > fax +46 18 471 4003
> > mats.karlsson_at_farmbio.uu.se
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: owner-nmusers_at_globomaxnm.com [mailto:owner-nmusers_at_globomaxnm.com]
> > On Behalf Of Ahmed Hawwa
> > Sent: Saturday, January 27, 2007 02:10
> > To: nmusers_at_globomaxnm.com
> > Subject: RE: [NMusers] Minimum patients number...
> >
> > Hi all,
> >
> > Thank you all indeed for the valuable commenets. I
> > have actually 19 patients only and I need to look into
> > the PK parameters of two metabolites.
> >
> > Minimum 10 patients per eta would mean 50-60 patients.
> > I'm sure this number would give optimal results but as
> > a matter of fact I don't think I would be able to
> > reach it.
> >
> > > I would suggest that you assess each case on its
> > > merits and determine the
> > > effectiveness of any proposed design using either
> > > simulation linked with
> > > estimation (which is tedious, slow, not optimal but
> > > often effective)
> >
> > Regarding using simultation do you mean to put certain
> > values of thetas and then run a simulation and compare
> > results with the actual concentrations or did I miss
> > the point?
> >
> > > or an
> > > information theoretic technique (such as optimal
> > > design).
> > > The optimal design software WinPOPT
> > > (www.winpopt.com), which is freely
> > > available, allows you to rapidly assess the
> > > effectiveness of various designs
> > > as well as optimize a design within your specific
> > > study constraints (e.g.
> > > clinic visit times etc).
> >
> > I think one of my study constrains is clinic visit
> > times since patients taking our drug are actually
> > outpatients and we are able to collect one sample only
> > at each clinic visit. would this software be of any
> > help??
> >
> > Looking to hear from you soon.
> >
> > Regards,
> > ahawwa
> >
> >
> >
> >
> > _______________________________________________________________________=
__
> >___ ________
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