请大家帮忙看看这个结果应该是用FE 还是RE

Note: the rank of the differenced variance matrix (0) does not equal the number of coefficients being tested (6); 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.
-------------+----------------------------------------------------------------
ln_size | .066395 .066395 0 0
gr | -.0458731 -.0458731 0 0
warr | .087804 .087804 0 0
dcost | -.0079675 -.0079675 0 0
gop | -.0012635 -.0012635 0 0
ln_repinc| .168674 .168674 0 0
------------------------------------------------------------------------------
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(0) = (b-B)'[(V_b-V_B)^(-1)](b-B)
= 0.00
Prob>chi2 = .
(V_b-V_B is not positive definite)

.