Hi,
I have a repeated measures data and I am fitting a non-linear mixed
effects model to it. The parametes in the non-linear model I would like
to have a multivariate normal distribution. This is because some of my
participants stopped early and so some of their parameters can't be
estimated well. I'd like to be able to "borrow" information from the
parameters that do fit well.
The model has been fitted before to a reasonably similar, larger data
set and I can use that as my prior information for the mean and variance
of the multivariate distribution. However, I don't know how to set the
degrees of freedom on the prior Wishart distribution to reflect my
(un)certainty. Is there a rule of thumb?
If it helps, the original data set contained information 18 people
with around 100 data points. My data set contains 49 people with 21 data
points.
Ta,
Megan
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