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st: Intreg - missing se


From   Simone Boyce <simonepeart@yahoo.com>
To   Stata <statalist@hsphsun2.harvard.edu>
Subject   st: Intreg - missing se
Date   Fri, 5 Mar 2004 11:00:16 -0800 (PST)

Hi,

I have panel data on medical expenditures by month by
patient over several years.  Given that many patients
incur no medical expenses in a month, I'm running
intreg in order to be able to correct the standard
errors by clustering by patient.  As a result,
however, I'm getting missing standard errors on some
variables.  I'm not sure why this is occurring so any
help you can offer would be appreciated.

Thanks,
Simone

An excerpt from my program follows:
Fitting constant-only model:
Iteration 0:   log likelihood = -14258.243
Iteration 1:   log likelihood = -14233.651
Iteration 2:   log likelihood = -14233.611
Iteration 3:   log likelihood = -14233.611
Fitting full model:
Iteration 0:   log likelihood = -14120.751
Iteration 1:   log likelihood = -14092.996
Iteration 2:   log likelihood = -14092.984
Iteration 3:   log likelihood = -14092.984
Interval regression
Number of obs   =       1721
                                                  Wald
chi2(78)   =       5.90
Log likelihood = -14092.984                       Prob
> chi2     =     1.0000
                               (standard errors
adjusted for clustering on id)
------------------------------------------------------------------------------
             |               Robust
             |      Coef.   Std. Err.      z
P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     max_epo |  -164.6891   291.8248    -0.56
0.573    -736.6553     407.277
     pre_epo |  -1042.706   675.1091    -1.54
0.122    -2365.895    280.4836
      n_neph |    95.0872          .        .
.            .           .
vas_access~1 |    1.67142   1.248917     1.34
0.181    -.7764116    4.119251
   sev_score |   554.5703   428.4049     1.29
0.195     -285.088    1394.229
    region_1 |   4848.412          .        .
.            .           .
    region_3 |  -564.5537   607.0004    -0.93
0.352    -1754.253    625.1452
    region_4 |  -236.4426   590.9987    -0.40
0.689    -1394.779    921.8936
    region_5 |  -56.82323   663.4045    -0.09
0.932    -1357.072    1243.426
    region_6 |   -249.867    603.322    -0.41
0.679    -1432.356    932.6224
    region_7 |  -83.41191   453.3813    -0.18
0.854     -972.023    805.1991
    region_8 |  -451.2196   629.4874    -0.72
0.473    -1684.992    782.5531
    region_9 |   942.6939   771.1849     1.22
0.222    -568.8008    2454.189
     dlockin |   868.6021   660.3181     1.32
0.188    -425.5976    2162.802
        dpos |   569.1639     476.98     1.19
0.233    -365.6997    1504.027
        dppo |   670.9701    556.107     1.21
0.228    -418.9795     1760.92
         chf |  -275.1132    319.468    -0.86
0.389    -901.2591    351.0326
        cirr |    2727.54   1875.542     1.45
0.146    -948.4542    6403.535
    diabetes |   27.53376   261.8082     0.11
0.916    -485.6009    540.6684
   hypertnsn |  -372.6621   393.7148    -0.95
0.344    -1144.329    399.0047
       trans |   123.8997   380.8696     0.33
0.745    -622.5909    870.3904
       chemo |   2092.798   1528.352     1.37
0.171    -902.7175    5088.313
        male |   181.9483    276.749     0.66
0.511    -360.4697    724.3663
  ageatindex |   71.00932   138.2606     0.51
0.608    -199.9765    341.9951
        age2 |  -1.087141          .        .
.            .           .
         mm4 |  -622.5777     934.07    -0.67
0.505    -2453.321    1208.166
         mm5 |  -201.6417          .        .
.            .           .
         mm6 |   1267.181   1191.833     1.06
0.288    -1068.769    3603.131
         mm7 |   -857.633   951.6563    -0.90
0.367    -2722.845    1007.579
         mm8 |  -965.2743   923.6236    -1.05
0.296    -2775.543    844.9947
         mm9 |   -680.489   1053.794    -0.65
0.518    -2745.887    1384.909
        mm10 |   98.51354   565.2734     0.17
0.862    -1009.402    1206.429
        mm11 |  -337.9866   768.3633    -0.44
0.660    -1843.951    1167.978
        mm12 |  -299.9577   763.3312    -0.39
0.694    -1796.059    1196.144
        mm13 |   3305.261   3137.035     1.05
0.292    -2843.215    9453.736
        mm14 |   1122.103   1143.299     0.98
0.326    -1118.723    3362.928
        mm15 |   959.0262   1117.877     0.86
0.391    -1231.973    3150.025
        mm16 |   1142.147   1213.986     0.94
0.347    -1237.222    3521.515
        mm17 |   830.9736   1068.596     0.78
0.437    -1263.437    2925.384
        mm18 |   3722.574   4284.308     0.87
0.385    -4674.516    12119.66
        mm19 |  -536.8562   672.7107    -0.80
0.425    -1855.345    781.6326
        mm20 |  -140.9105   671.1563    -0.21
0.834    -1456.353    1174.532
        mm21 |    1079.41   1127.801     0.96
0.339    -1131.039    3289.859
        mm22 |   75.58293   699.3105     0.11
0.914     -1295.04    1446.206
        mm23 |   146.1172   847.5345     0.17
0.863     -1515.02    1807.254
        mm24 |   237.6426   773.9678     0.31
0.759    -1279.306    1754.592
        mm25 |   727.6342   783.8668     0.93
0.353    -808.7166    2263.985
        mm26 |   395.0451   688.7651     0.57
0.566    -954.9097        1745
        mm27 |   486.1328   701.1925     0.69
0.488    -888.1793    1860.445
        mm28 |   1248.766   1077.945     1.16
0.247    -863.9666    3361.499
        mm29 |   714.2825   827.6684     0.86
0.388    -907.9178    2336.483
        mm30 |   471.1459   696.3958     0.68
0.499    -893.7648    1836.057
        mm31 |  -9.212793   587.8447    -0.02
0.987    -1161.367    1142.942
        mm32 |   274.1597   590.3528     0.46
0.642    -882.9105     1431.23
        mm33 |   212.8656   606.9387     0.35
0.726    -976.7125    1402.444
        mm34 |   438.5759    634.901     0.69
0.490    -805.8072    1682.959
        mm35 |  -105.9359   558.4603    -0.19
0.850    -1200.498    988.6262
        mm36 |  -179.4214   537.0638    -0.33
0.738    -1232.047    873.2043
        mm37 |   597.0361   687.0661     0.87
0.385    -749.5887    1943.661
        mm38 |   548.8999   673.7504     0.81
0.415    -771.6266    1869.426
        mm39 |   699.3571   726.3962     0.96
0.336    -724.3532    2123.067
        mm40 |   487.3255   617.6076     0.79
0.430    -723.1631    1697.814
        mm41 |   1575.052   1155.193     1.36
0.173    -689.0844    3839.188
        mm42 |  -155.3469   530.8564    -0.29
0.770    -1195.806    885.1125
        mm43 |   51.08252   564.6187     0.09
0.928     -1055.55    1157.715
        mm44 |   119.5142   569.8381     0.21
0.834    -997.3479    1236.376
        mm45 |   263.1357   575.8147     0.46
0.648    -865.4404    1391.712
        mm46 |   235.8872   574.7066     0.41
0.681    -890.5171    1362.292
        mm47 |  -329.0518   583.1212    -0.56
0.573    -1471.948    813.8448
        mm48 |   -995.237   805.7808    -1.24
0.217    -2574.538    584.0643
        mm49 |  -459.7242   597.8082    -0.77
0.442    -1631.407    711.9582
        mm50 |   241.0219   656.1713     0.37
0.713     -1045.05    1527.094
        mm51 |    -3.8692   640.1957    -0.01
0.995     -1258.63    1250.891
        mm52 |   101.8969   576.5746     0.18
0.860    -1028.168    1231.962
        mm53 |   909.3605   1188.337     0.77
0.444    -1419.738    3238.459
        mm54 |  -622.1598   745.0753    -0.84
0.404    -2082.481     838.161
        mm55 |  -202.6312   605.8447    -0.33
0.738    -1390.065    984.8026
        mm56 |   451.7741   862.7561     0.52
0.601    -1239.197    2142.745
        mm57 |   1500.307   1628.656     0.92
0.357    -1691.799    4692.414
        mm58 |   1684.418   1593.234     1.06
0.290    -1438.264    4807.099
        mm59 |   796.8443   817.5986     0.97
0.330    -805.6194    2399.308
        mm60 |   2312.352   2071.913     1.12
0.264    -1748.524    6373.228
       _cons |  -495.3673   3248.196    -0.15
0.879    -6861.714    5870.979
-------------+----------------------------------------------------------------
      /sigma |   3163.778
1925.315                     -609.7704    6937.326
------------------------------------------------------------------------------
  Observation summary:      1468     uncensored
observations
                             253  left-censored
observations
                               0 right-censored
observations
                               0       interval
observations





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