Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: inverse logit of gamma and xtfrontier


From   Scott Merryman <scott.merryman@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: inverse logit of gamma and xtfrontier
Date   Fri, 17 Feb 2012 12:34:58 -0600

In the -xtfrontier- command (stochastic frontier models for panel
data), the gamma parameter is parameterized in terms of the inverse
logit of gamma and Stata reports the hypothesis test that the inverse
logit of gamma is 0.

Does this reported hypothesis test has any substantive meaning?  It
not clear to me what inferences one can draw if the inverse logit of
gamma is not statistically different from 0 (and therefore gamma is
0.50).

To test for existence of inefficiency effects, following Battese and
Coelli (1992), one would need to constrain the three parameters mu =
eta = gamma = 0 and use a likelihood ratio test:

webuse xtfrontier1
constraint 1 [eta]_cons = 0
constraint 2 [mu]_cons = 0
constraint 3 [ilgtgamma]_cons = -100 /* making gamma close to zero */
xtfrontier lnwidgets lnmachines lnworkers, tvd
est store A
xtfrontier lnwidgets lnmachines lnworkers, tvd constraints(1 2 3)
lrtest A ., stat
disp (1 - chi2(1, r(chi2)))*.5


Thank you,
Scott


Battese and Coelli. 1992 "Frontier production functions, technical
efficiency and panel data: With application to paddy farmers"  Journal
of Productivity Analysis,Volume 3, Numbers 1-2.
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index