--- Ehsan Rahman <[email protected]> wrote:
> Hi I am trying to do Terza's 2-step method of moments estimation in
> Stata, however I am getting a strange error message. When I run it as
> it is below, with "1-normal(t)" in the denominator of the second term
> in the correction equation, I get the following error: "starting
> values invalid or some RHS variables have missing values."
> If however, I simlply change "1-normal(t)" to ".99999-normal(t)" the
> estimation runs as expected.
Looks like you've been bitten by a precision problem. A calculation
like 1-normal(t) may cause numerical problems, a more stable version of
this calculation is normal(-t). A clear explanation can be found in
William Gould (2006) "Mata matters: precision", The Stata Journal,
6(4), pp. 550-560.
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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