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st: Randomized cross-over trial xtmixed og anova for repeated measurements


From   Christian Trolle <CHRISTIAN.TROLLE@ki.au.dk>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: Randomized cross-over trial xtmixed og anova for repeated measurements
Date   Mon, 2 Dec 2013 07:57:48 +0000

Dear Statalist

I want to fit a ANOVA model for repeated measurements or an mixed linear model with xtmixed. 
Comments on the design.
1. 7 patients seen at three visits randomized to three different interventions before each visit eg. fasting, exercise etc.
2. Main outcome is continuous, measured 4 times at each visit (0, 30 min, 60 min, 120 min).
3. The test should account for an unstructered covariance matrix

I have tried to fit a multivariate model like this:

egen VisitPatient = group(Visit Patient), label
xi: xtmixed Outcome bn.Time#bn.Visit || VisitPatient: i.Time, cov(un) technique(dfp)

I the use a likelihood ratio test to compare models.

The dataset could look like this
Visit	Patient	Outcome	Time
0	1	y	1
0	1	y	2
0	1	y	3
0	1	y	4
0	2	y	1
0	2	y	2
0	2	y	3
0	2	y	4
0	3	y	1
0	3	y	2
0	3	y	3
0	3	y	4
0	4	y	1
0	4	y	2
0	4	y	3
0	4	y	4
0	5	y	1
0	5	y	2
0	5	y	3
0	5	y	4
0	6	y	1
0	6	y	2
0	6	y	3
0	6	y	4
0	7	y	1
0	7	y	2
0	7	y	3
0	7	y	4
1	1	y	1
1	1	y	2
1	1	y	3
1	1	y	4
1	2	y	1
1	2	y	2
1	2	y	3
1	2	y	4
1	3	y	1
1	3	y	2
1	3	y	3
1	3	y	4
1	4	y	1
1	4	y	2
1	4	y	3
1	4	y	4
1	5	y	1
1	5	y	2
1	5	y	3
1	5	y	4
1	6	y	1
1	6	y	2
1	6	y	3
1	6	y	4
1	7	y	1
1	7	y	2
1	7	y	3
1	7	y	4
2	1	y	1
2	1	y	2
2	1	y	3
2	1	y	4
2	2	y	1
2	2	y	2
2	2	y	3
2	2	y	4
2	3	y	1
2	3	y	2
2	3	y	3
2	3	y	4
2	4	y	1
2	4	y	2
2	4	y	3
2	4	y	4
2	5	y	1
2	5	y	2
2	5	y	3
2	5	y	4
2	6	y	1
2	6	y	2
2	6	y	3
2	6	y	4
2	7	y	1
2	7	y	2
2	7	y	3
2	7	y	4


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