Code:
reg sbpd ib6.group i.black_or_not ib6.group#i.black_or_not i.sex age stratum urpot, cformat(%9.2f) vce(cluster clinic) testparm i.black_or_not#i.group contrast r.black_or_not@group, cformat(%9.2f)
Code:
Linear regression Number of obs = 884
F(2, 3) = .
Prob > F = .
R-squared = 0.1284
Root MSE = 10.644
(Std. err. adjusted for 4 clusters in clinic)
---------------------------------------------------------------------------------------
| Robust
sbpd | Coefficient std. err. t P>|t| [95% conf. interval]
----------------------+----------------------------------------------------------------
group |
Acebutolol | -8.00 1.87 -4.27 0.024 -13.96 -2.04
Amlodipine | -6.47 1.30 -4.97 0.016 -10.60 -2.33
Chlorthalidone | -7.51 2.29 -3.28 0.046 -14.80 -0.22
Doxazosin | -5.61 1.24 -4.52 0.020 -9.56 -1.66
Enalapril | -5.77 2.56 -2.26 0.109 -13.90 2.37
|
black_or_not |
Black | 3.10 1.55 2.01 0.139 -1.82 8.02
|
group#black_or_not |
Acebutolol#Black | 0.27 0.70 0.39 0.722 -1.95 2.50
Amlodipine#Black | -0.71 0.81 -0.88 0.444 -3.29 1.86
Chlorthalidone#Black | -4.16 2.25 -1.84 0.162 -11.33 3.02
Doxazosin#Black | 3.46 2.26 1.53 0.223 -3.74 10.67
Enalapril#Black | 1.35 4.73 0.29 0.793 -13.71 16.42
|
2.sex | -0.55 0.49 -1.12 0.345 -2.10 1.01
age | -0.27 0.05 -5.71 0.011 -0.42 -0.12
stratum | 2.15 0.65 3.31 0.045 0.08 4.22
urpot | -0.04 0.05 -0.82 0.471 -0.21 0.13
_cons | 2.46 3.59 0.68 0.543 -8.95 13.86
---------------------------------------------------------------------------------------
.
. testparm i.black_or_not#i.group
( 1) 1.group#2.black_or_not = 0
( 2) 2.group#2.black_or_not = 0
( 3) 3.group#2.black_or_not = 0
( 4) 4.group#2.black_or_not = 0
( 5) 5.group#2.black_or_not = 0
Constraint 1 dropped
Constraint 2 dropped
F( 3, 3) = 15.80
Prob > F = 0.0242
.
. contrast r.black_or_not@group, cformat(%9.2f)
Contrasts of marginal linear predictions
Margins: asbalanced
------------------------------------------------------------------------
| df F P>F
-------------------------------------+----------------------------------
black_or_not@group |
(Black vs Not Black) Acebutolol | 1 7.58 0.0705
(Black vs Not Black) Amlodipine | 1 6.64 0.0820
(Black vs Not Black) Chlorthalidone | 1 0.34 0.6012
(Black vs Not Black) Doxazosin | 1 27.40 0.0136
(Black vs Not Black) Enalapril | 1 1.52 0.3059
(Black vs Not Black) Placebo | 1 4.02 0.1386
Joint | 3 19.14 0.0185
|
Denominator | 3
------------------------------------------------------------------------
--------------------------------------------------------------------------------------
| Contrast Std. err. [95% conf. interval]
-------------------------------------+------------------------------------------------
black_or_not@group |
(Black vs Not Black) Acebutolol | 3.37 1.23 -0.53 7.28
(Black vs Not Black) Amlodipine | 2.39 0.93 -0.56 5.34
(Black vs Not Black) Chlorthalidone | -1.06 1.81 -6.82 4.71
(Black vs Not Black) Doxazosin | 6.57 1.25 2.57 10.56
(Black vs Not Black) Enalapril | 4.46 3.62 -7.06 15.97
(Black vs Not Black) Placebo | 3.10 1.55 -1.82 8.02
--------------------------------------------------------------------------------------
.I am surprised to find out that the interaction for the main effect of race "Black" is the same coefficient as the contrast of "Black vs. not Black Placebo". Both are highlighted in red text above. Any guidance on my code and/or output will be appreciated.
Al Bothwell
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