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没有问题
可以用
. xtmixed y x || id:, ml vce(robust)
Performing EM optimization:
Performing gradient-based optimization:
Iteration 0: log pseudolikelihood = -1014.9268
Iteration 1: log pseudolikelihood = -1014.9268
Computing standard errors:
Mixed-effects regression Number of obs = 432
Group variable: id Number of groups = 48
Obs per group:
min = 9
avg = 9.0
max = 9
Wald chi2(1) = 4552.32
Log pseudolikelihood = -1014.9268 Prob > chi2 = 0.0000
(Std. Err. adjusted for 48 clusters in id)
------------------------------------------------------------------------------
| Robust
y | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
x | 6.209896 .0920382 67.47 0.000 6.029504 6.390287
_cons | 19.35561 .4038676 47.93 0.000 18.56405 20.14718
------------------------------------------------------------------------------
------------------------------------------------------------------------------
| Robust
Random-effects Parameters | Estimate Std. Err. [95% Conf. Interval]
-----------------------------+------------------------------------------------
id: Identity |
sd(_cons) | 3.849352 .3580731 3.207801 4.619211
-----------------------------+------------------------------------------------
sd(Residual) | 2.093625 .152043 1.815862 2.413874
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