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st: Number of constraints bellow number of variables in svy:regress


From   Ángel Rodríguez Laso <angelrlaso@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Number of constraints bellow number of variables in svy:regress
Date   Wed, 9 May 2012 18:03:39 +0200

Dear statalisters,

I want to ask you about a result that is puzzling me. I'm working with
Stata 9.2.

I've conducted a regression analysis in a svy scenario, whose results
are bellow. Imc is  the continuous variable body mass index, ccaa are
regions and edadcen is age centered. Stata is not providing the result
of the F test. When I click on the F test, it explains that the number
of variables exceeds the number of constraints, but I do not
understand why it limits the number of constraints bellow the actual
number of variables (30 constraints instead of 33). There is no
collinearity among regressors and no variable is non-zero for just a
single cluster.

I would appreciate any suggestions.

Best regards,

Angel Rodriguez-Laso



. svyset secciond

pweight: <none>
VCE: linearized
Strata 1: <one>
SU 1: secciond
FPC 1: <zero>


. xi: svy: regress imc i.ccaa*edadcen
i.ccaa            _Iccaa_1-17         (naturally coded; _Iccaa_1 omitted)
i.ccaa*edadcen    _IccaXedad_#        (coded as above)
(running regress on estimation sample)

Survey: Linear regression

Number of strata   =         1                  Number of obs      =      1376
Number of PSUs     =       221                  Population size    =      1376
Design df          =       220
F(  30,    191)    =         .
Prob > F           =         .
R-squared          =    0,0417


Linearized
          imc       Coef.       Std. Err.      t          P>t     [95%
Conf. Interval]

_Iccaa_2     ,848663   ,8027559     1,06   0,292    -,7334128    2,430739
_Iccaa_3   -,3322651   1,063326    -0,31   0,755    -2,427874    1,763344
_Iccaa_4   -1,353941   ,4974052    -2,72   0,007     -2,33423   -,3736519
_Iccaa_5    ,5805167   ,6889628     0,84   0,400     -,777295    1,938328
_Iccaa_6   -,5940687   1,242126    -0,48   0,633    -3,042058    1,853921
_Iccaa_7   -,9402941   ,6984523    -1,35   0,180    -2,316808    ,4362197
_Iccaa_8   -,2953288    ,777433    -0,38   0,704    -1,827498    1,236841
_Iccaa_9   -,1577222   ,5504684    -0,29   0,775    -1,242588     ,927144
_Iccaa_10    ,5662263   ,7136282     0,79   0,428    -,8401962    1,972649
_Iccaa_11    ,4781356   ,5046006     0,95   0,344    -,5163341    1,472605
_Iccaa_12   -,0534289   ,6041021    -0,09   0,930    -1,243997    1,137139
_Iccaa_13   -1,216056   ,4847292    -2,51   0,013    -2,171363   -,2607486
_Iccaa_14    ,6052608   1,040884     0,58   0,562     -1,44612    2,656642
_Iccaa_15    -2,13085   ,3863896    -5,51   0,000    -2,892349   -1,369351
_Iccaa_16   -,8689058   ,4407194    -1,97   0,050    -1,737478   -,0003336
_Iccaa_17   -,6012072   ,5552926    -1,08   0,280    -1,695581    ,4931665
edadcen       ,0369179   ,0245296     1,51   0,134    -,0114251    ,0852609
_IccaXedad_2    ,0426598   ,0616997     0,69   0,490    -,0789384     ,164258
_IccaXedad_3    ,1706813   ,0702684     2,43   0,016     ,0321959    ,3091668
_IccaXedad_4   -,0046423   ,0547784    -0,08   0,933    -,1125999    ,1033154
_IccaXedad_5   -,0326074   ,0476211    -0,68   0,494    -,1264594    ,0612445
_IccaXedad_6   -,0962989    ,147651    -0,65   0,515    -,3872904    ,1946926
_IccaXedad_7    ,0133227   ,0372468     0,36   0,721    -,0600836     ,086729
_IccaXedad_8   -,0887991   ,0477911    -1,86   0,064     -,182986    ,0053879
_IccaXedad_9   -,0150726   ,0401828    -0,38   0,708     -,094265    ,0641198
_IccaXeda~10    ,1224726   ,0717207     1,71   0,089     -,018875    ,2638202
_IccaXeda~11    ,0020611    ,042724     0,05   0,962    -,0821395    ,0862617
_IccaXeda~12   -,0204515   ,0543341    -0,38   0,707    -,1275335    ,0866305
_IccaXeda~13    ,0511209   ,0301568     1,70   0,091    -,0083123    ,1105541
_IccaXeda~14   -,1436726   ,0628606    -2,29   0,023    -,2675587   -,0197865
_IccaXeda~15   -,0596086   ,0248327    -2,40   0,017    -,1085491   -,0106681
_IccaXeda~16    ,0018936   ,0320483     0,06   0,953    -,0612673    ,0650545
_IccaXeda~17   -,0479953   ,0394831    -1,22   0,225    -,1258088    ,0298182
_cons                 28,83275   ,3859916    74,70   0,000
28,07203    29,59346
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