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The first part of this chapter, on 1-1 matched studies, makes use of the plowbwt file.
use plowbwt
Table 7.1 -- page 193
xi i.race
i.race Irace_1-3 (naturally coded; Irace_1 omitted)
clogit low Irace_2 Irace_3 smoke ht ui ptd lwt, group(pairno)
Iteration 0: log likelihood = -34.044665
Iteration 1: log likelihood = -27.050067
Iteration 2: log likelihood = -25.88921
Iteration 3: log likelihood = -25.795206
Iteration 4: log likelihood = -25.794271
Iteration 5: log likelihood = -25.794271
Conditional (fixed-effects) logistic regression Number of obs = 112
LR chi2(7) = 26.04
Prob > chi2 = 0.0005
Log likelihood = -25.794271 Pseudo R2 = 0.3355
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
Irace_2 | .5713643 .6896449 0.828 0.407 -.7803149 1.923044
Irace_3 | -.0253148 .6992044 -0.036 0.971 -1.39573 1.345101
smoke | 1.400656 .6278396 2.231 0.026 .1701131 2.631199
ht | 2.361152 1.086128 2.174 0.030 .2323797 4.489924
ui | 1.401929 .6961585 2.014 0.044 .0374836 2.766375
ptd | 1.808009 .7886502 2.293 0.022 .2622829 3.353735
lwt | -.0183757 .0100806 -1.823 0.068 -.0381333 .0013819
------------------------------------------------------------------------------
Table 7.2 -- page 193
clogit low smoke ht ui ptd lwt, group(pairno)
Iteration 0: log likelihood = -34.258826
Iteration 1: log likelihood = -27.380314
Iteration 2: log likelihood = -26.315212
Iteration 3: log likelihood = -26.237479
Iteration 4: log likelihood = -26.236872
Iteration 5: log likelihood = -26.236872
Conditional (fixed-effects) logistic regression Number of obs = 112
LR chi2(5) = 25.16
Prob > chi2 = 0.0001
Log likelihood = -26.236872 Pseudo R2 = 0.3241
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
smoke | 1.479564 .5620191 2.633 0.008 .3780272 2.581102
ht | 2.329361 1.002549 2.323 0.020 .3644009 4.294322
ui | 1.344895 .693843 1.938 0.053 -.0150127 2.704802
ptd | 1.670594 .7468062 2.237 0.025 .206881 3.134308
lwt | -.0150834 .0081465 -1.852 0.064 -.0310503 .0008834
------------------------------------------------------------------------------
Table 7.5 -- page 197
clogit low Irace_2 smoke ht ui ptd lwt, group(pairno)
Iteration 0: log likelihood = -34.084323
Iteration 1: log likelihood = -27.047778
Iteration 2: log likelihood = -25.889241
Iteration 3: log likelihood = -25.795845
Iteration 4: log likelihood = -25.794926
Iteration 5: log likelihood = -25.794926
Conditional (fixed-effects) logistic regression Number of obs = 112
LR chi2(6) = 26.04
Prob > chi2 = 0.0002
Log likelihood = -25.794926 Pseudo R2 = 0.3355
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
Irace_2 | .5822724 .6207082 0.938 0.348 -.6342933 1.798838
smoke | 1.410799 .5621771 2.510 0.012 .3089521 2.512646
ht | 2.351335 1.05135 2.236 0.025 .2907277 4.411943
ui | 1.399261 .6922439 2.021 0.043 .0424881 2.756034
ptd | 1.807481 .7889523 2.291 0.022 .2611626 3.353799
lwt | -.0182215 .0091299 -1.996 0.046 -.0361158 -.0003272
------------------------------------------------------------------------------
The second part of this chapter, on 1-m matched studies, makes use of the mlowbwt file.
use mlowbwt
Figure 7.8 -- page 203
clogit low smoke ht ui ptd lwt, group(str)
Iteration 0: log likelihood = -37.125252
Iteration 1: log likelihood = -32.363492
Iteration 2: log likelihood = -32.339464
Iteration 3: log likelihood = -32.339447
Conditional (fixed-effects) logistic regression Number of obs = 116
LR chi2(5) = 15.73
Prob > chi2 = 0.0077
Log likelihood = -32.339447 Pseudo R2 = 0.1956
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
smoke | .5535844 .4889295 1.132 0.258 -.4046999 1.511869
ht | .0982997 1.39487 0.070 0.944 -2.635595 2.832194
ui | .5253556 .5491917 0.957 0.339 -.5510404 1.601752
ptd | 1.532963 .6382403 2.402 0.016 .2820354 2.783891
lwt | -.0054817 .0091466 -0.599 0.549 -.0234086 .0124452
------------------------------------------------------------------------------
Figure 7.10 -- page 204
/* create dichotomous variable lwd from variable lwt */
generate lwd=(lwt>110)
clogit low smoke ht ui ptd lwd, group(str)
Iteration 0: log likelihood = -37.118989
Iteration 1: log likelihood = -32.096809
Iteration 2: log likelihood = -32.051232
Iteration 3: log likelihood = -32.051174
Conditional (fixed-effects) logistic regression Number of obs = 116
LR chi2(5) = 16.30
Prob > chi2 = 0.0060
Log likelihood = -32.051174 Pseudo R2 = 0.2028
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
smoke | .5551283 .4832855 1.149 0.251 -.3920939 1.50235
ht | -.0258181 1.30567 -0.020 0.984 -2.584884 2.533248
ui | .5002357 .5408307 0.925 0.355 -.5597729 1.560244
ptd | 1.525277 .6359686 2.398 0.016 .2788018 2.771753
lwd | -.5192773 .5252275 -0.989 0.323 -1.548704 .5101497
------------------------------------------------------------------------------
Figure 7.11 -- page 204
clogit low smoke ui ptd lwd, group(str)
Iteration 0: log likelihood = -37.125783
Iteration 1: log likelihood = -32.097091
Iteration 2: log likelihood = -32.051427
Iteration 3: log likelihood = -32.05137
Conditional (fixed-effects) logistic regression Number of obs = 116
LR chi2(4) = 16.30
Prob > chi2 = 0.0026
Log likelihood = -32.05137 Pseudo R2 = 0.2028
------------------------------------------------------------------------------
low | Coef. Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
smoke | .5542481 .4812274 1.152 0.249 -.3889402 1.497436
ui | .5000503 .5407949 0.925 0.355 -.5598883 1.559989
ptd | 1.525917 .6351749 2.402 0.016 .2809971 2.770837
lwd | -.5213152 .5151962 -1.012 0.312 -1.531081 .4884508
------------------------------------------------------------------------------
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