chi2(4) = (b-B)'[(V_b-V_B)^(-1)](b-B)
= -198.36 chi2<0 ==> model fitted on these
data fails to meet the asymptotic
assumptions of the Hausman test;
see suest for a generalized test
请问hausman 检验为负值怎么处理啊!!大侠们求救!!