st: repeated measures ANOVA to MANOVA

[Ricardo Ovaldia <ovaldia@yahoo.com>]

I have data on 23 patients that were evaluated using three competing medical methods. I used repeated measures ANOVA and reported the Huynh-Feldt corrected p-value. A reviewer suggested that it would be better to do a MANOVA. However, when I try this,  Stata reports the error:

. manova m1 m2 m3=id
matrix not positive definite
insufficient residual degrees of freedom for this multivariate model

Any help will be appreciated.
Ricardo

Here is the data:
. cl id m1 m2 m3

           id     m1     m2     m3
  1.      106   22.2   30.6   13.9
  2.      111   26.4   32.2   14.6
  3.      119   23.6   28.9   26.7
  4.      122   27.4   38.0   28.9
  5.      130   17.5   24.5   41.4
  6.      131   18.4   21.5   20.2
  7.      133   28.1   28.1   22.3
  8.      135   33.5   38.5   29.9
  9.      140   18.9   25.7   15.1
 10.      144   21.2   28.3   37.0
 11.      149   18.8   25.6   15.5
 12.      152   22.4   31.5   28.5
 13.      153   21.5   28.6   22.5
 14.      158   27.9   37.6   37.2
 15.      167   30.1   42.3   24.0
 16.      168   28.5   36.9   32.4
 17.      171   23.5   36.7   27.8
 18.      176   24.6   24.5   25.8
 19.      180   29.4   30.3   15.2
 20.      188   23.2   24.6    9.1
 21.      191   25.7   31.7   31.2
 22.      192   20.1   19.7    8.2
 23.      194   23.4   27.7    6.0


Ricardo Ovaldia, MS
Statistician 
Oklahoma City, OK
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