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st: Unbalanced repeated measures analysis question


From   K Jensen <k.x.jensen@gmail.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: Unbalanced repeated measures analysis question
Date   Wed, 21 Jul 2010 15:01:41 +0100

Hi

I have data on measuring a biological property for three different
methods plus a gold standard. Different people were trained in each
method (1,2 or 3) and measured the same subjects during different
sessions, together with the gold standard measurement.

So the data look like
SubjectID MeasurerID MeasurerType Result GoldStandard  Diff
1         1          1            95     99            -4
1         2          3            102    99            +3
1         3          2            92     99            -7
...
1        10          3            105    99            +6
2         1          3             98   100            -2
...

Sometimes patients would be called in to see the consultant and so
missed for a particular measurer, but otherwise all the measurers
would measure all the patients seen in a particular session. Different
sets of measurers (but all trained by methods 1,2 or 3) were used on
each session (individual measurers 1-10 on session 1, 11-20 on session
2 etc).

The gold standard measurements on each session are roughly normally
distributed, as are the differences from the gold standard. We are
interested in the accuracy of each of the three methods.

Is it OK to do some sort of repeated measures ANOVA here, with an
unbalanced design? If it is what would be the syntax (Stata 10)? Sorry
to sound pathetic but I just can't get the anova command with the
repeated option to work here.

Is there a better measure to use than the difference to reflect the
fact that we are interested in a comparison with a gold standard?

Thankyou
Karin
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