.
. 为什么会得到负的卡方检验值呢?这种情况下可否认为固定效应是合理的呢?
. hausman fe
Note: the rank of the differenced variance matrix (9) does not equal the number of coefficients being
tested (10); be sure this is what you expect, or there may be problems computing the test. Examine
the output of your estimators for anything unexpected and possibly consider scaling your variables
so that the coefficients are on a similar scale.
---- Coefficients ----
| (b) (B) (b-B) sqrt(diag(V_b-V_B))
| fe re Difference S.E.
-------------+----------------------------------------------------------------
dar | -.0442345 -.0527817 .0085472 .004907
fsize | -.2448338 .2065122 -.451346 .5233349
gsale | .0056962 .0061054 -.0004092 .0002903
herf | .0012748 .0004844 .0007904 .0003361
herf2 | -1.18e-07 -4.56e-08 -7.20e-08 3.70e-08
dumt2 | 1.329218 1.295918 .0333008 .0247267
dumt3 | 2.502135 2.461852 .0402829 .0260247
dumt4 | 3.334255 3.26244 .0718158 .028847
dumt5 | 3.161338 3.074924 .0864145 .0404706
dumt6 | 3.496019 3.413124 .0828951 .0449345
------------------------------------------------------------------------------
b = consistent under Ho and Ha; obtained from xtreg
B = inconsistent under Ha, efficient under Ho; obtained from xtreg
Test: Ho: difference in coefficients not systematic
chi2(9) = (b-B)'[(V_b-V_B)^(-1)](b-B)
= -21.43 chi2<0 ==> model fitted on these
data fails to meet the asymptotic
assumptions of the Hausman test;
see suest for a generalized test



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