Yes. Also no 'treatment' here. Just have a collection
of measures made during 'routine physicals' on these
animals, different numbers of measures per animal,
data set in the long form, and want to take a stab at
stating what are 'normal' values--the mean, sd, also
MEDIAN, etc--for this animal.
"FEIVESON, ALAN H. (AL) (JSC-SD) (NASA)" wrote:
>
> Kate,
>
> Nick suggests we don't have enough information to
properly answer your
> questiion.
> I would like to add that specifically, we need to
know:
>
> a) but what sort of model for your data you are
assuming
> b) what paarameters in the model you are trying to
estimate. I'll take a
> guess:
>
> a) y_ij = mu + a_i + e_ij = j-th measurement on i-th
animal
>
> mu is mean creatinine level for a population of
animals undergoing (this)
> experiment
> mu + a_i is mean creatinine level specific to the
i-th animal
> a_i ~ N(0,siga^2)
> e_ij is random variation of measured creatinine
level about the mean for the
> i-th animal
> e_ij ~ N(0, sige^2)
>
> b) you wish to estimate mu and siga
>
> Is this correct? - If not - please give your
interpretation of what a) and
> b) are.
>
> Al Feiveson
>
> -----Original Message-----
> From: Nick Cox [mailto:[email protected]]
> Sent: Thursday, January 02, 2003 8:29 AM
> To: [email protected]
> Subject: st: RE: mean and median with multiple
measures
>
> Kate
>
> > I have about 200 measures of creatinine but they
are
> > from only 25 animals. How do I calculate the mean
and
> > the median creatinine values in Stata?
>
> Several answers already; but if they don't
> provide an answer I think you will need
> to tell us more about your data structure.
> What variables and what observations do
> you have?
>
> Nick
> [email protected]
>
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