On Sat, Mar 16, 2013 at 6:49 PM, megan rossi <megan_rossi@msn.com> wrote:
> Yes The surgery was 1-3weeks after the baselines were taken...a fairly strict protocol. Then one year follow up and two year follow up...variable a &b were both low at baseline (still detectable and possibly correlated) but rise following surgery so are high at year 1 and year 2...perhaps best to just combine year 1 and 2 as if they're both high a correlation would be easier to find then if they're both low?
>
I don't think I'd combine them. You have different measures and that
should be respected.
To me the fact that this is longitudinal means that there's a clear
logical priority. I'd consider the first measurement as "causal" of
the second one, at least in some respect. So I'm not sure a pure
correlation makes sense. But I'd like to hear what others might say.
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