# 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

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
------------------------------------------------------------------------------
|               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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```