st: ANOVA repeated measures

[Rune Nielsen <nielsenrune@me.com>]

Dear statalist members,

We have done a simple pilot study where we measure the number of bacteria on the tip of a bronchoscope two times on the same 20 subjects. Half of these subjects have received an intervention to reduce the number of bacteria. So in a long dataset with 40 observations  I have the following variables

Idnr - subject ID

meas - binary variable indicating first (=1) or second (=2) measurement

flush - binary variable whether the subject have received (=1) or not (=0) the intervention

bal - measurement of bacterial load

What I would like to do, is to test whether the difference between measurement 1 and measurement 2 is  depending on whether they have received the intervention. I've tried various ANOVA syntaxes, but my limited knowledge won't quite get me there. 

Probably this reveals my incompetence, but nevertheless I hope for an answer that is understandable for a non-statisician.

Best wishes,

Rune Nielsen 

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Rune Nielsen, MD, PhD, postdoctoral fellow
Institute of Medicine
Department of Thoracic Medicine
Haukeland University Hospital
N-5021 Bergen
Norway