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st: Re: Contrasts


From   Edward Ridell <edwardridell@ymail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: Contrasts
Date   Mon, 23 Mar 2009 16:02:00 +0000 (GMT)

Following this anova:
. anova f sys tc sys*tc

                           Number of obs =     180     R-squared     =  0.9399
                           Root MSE      = 1.61981     Adj R-squared =  0.9359

                  Source |  Partial SS    df       MS           F     Prob > F
              -----------+----------------------------------------------------
                   Model |  6891.18382    11  626.471256     238.77     0.0000
                         |
                     sys |  1347.15634     2  673.578172     256.72     0.0000
                      tc |  4939.60999     3  1646.53666     627.54     0.0000
                  sys*tc |  604.417487     6  100.736248      38.39     0.0000
                         |
                Residual |  440.796853   168  2.62379079   
              -----------+----------------------------------------------------
                   Total |  7331.98067   179  40.9607859   
I want to compare systems 1,2 & 3 at time 4. The design matrix is
. test, showorder

 Order of columns in the design matrix
      1: _cons
      2: (sys==1)
      3: (sys==2)
      4: (sys==3)
      5: (tc==1)
      6: (tc==2)
      7: (tc==3)
      8: (tc==4)
      9: (sys==1)*(tc==1)
     10: (sys==1)*(tc==2)
     11: (sys==1)*(tc==3)
     12: (sys==1)*(tc==4)
     13: (sys==2)*(tc==1)
     14: (sys==2)*(tc==2)
     15: (sys==2)*(tc==3)
     16: (sys==2)*(tc==4)
     17: (sys==3)*(tc==1)
     18: (sys==3)*(tc==2)
     19: (sys==3)*(tc==3)
     20: (sys==3)*(tc==4)
and I tried the following:
mat input c2 = (0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,-1,0,0,0,0 \ 0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,-1 \ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,-1)
. test, test(c2)

 ( 1)  sys[1]*tc[4] - sys[2]*tc[4] = 0
 ( 2)  sys[1]*tc[4] - sys[3]*tc[4] = 0
 ( 3)  sys[2]*tc[4] - sys[3]*tc[4] = 0
       Constraint 1 dropped
       Constraint 2 dropped
       Constraint 3 dropped

. test, test(c2) mtest(sidak)
_mtest: 0 valid tests
r(198);

Is there anyway that I can carry out this comparison? 
I am usung Stata 10.

Ted.


      

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