Dear listers,
In the frontier output for Stata there is a test called chibar2 (LR test for
sigma_u=0).
The help explanation implies that the test is based on the assumption that
the inefficiency term is "a 50:50 mixture of a chisquare with no degrees of
freedom (i.e. a point mass at zero) and a chisquare with 1 degree of
freedom."
This seems to be incompatible with the half-normal distribution assumed by
most software, including stata, which does not have a point mass at zero.
Can somebody explain this apparent discrepancy
Thanks to you all
Maria
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