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st: Help with Frontier output - Chibar test

From   "maria croppenstedt" <>
Subject   st: Help with Frontier output - Chibar test
Date   Tue, 27 Sep 2005 14:48:24 +0200

Dear listers,

In the frontier output for Stata there is a test called chibar2 (LR test for

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

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

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