# st: Intreg - missing se

 From Simone Boyce To Stata 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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