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help for ^gwhet^                                    (Gimpavido@@worldbank.org)
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Likelihood Ratio test for groupwise heteroschedasticity 
----------------------------

	^gwhet^ var, ^i^(^idx^)


Description
-----------

^gwhet^ Performs a likelihood ratio test for groupwise heteroschedasticity
	on the variable ^var^ when groups are defined bu the index variable
	^idx^. idx may contain string, numeric, or both string and nu-
	meric variables. Missing values in idx (either ^.^ or "") are
	treated like any other group number. var has to be an OLS residual as
	mean(var) is assumed to be = 0. 
	N.B. : Version 1.1.0 uses MLE for the group variances while version 
	1.0.0 uses sample equivalent with group means different from zero.

References: 	Greene W.H. 
		Econometric Analysis.
		Prentice Hall, 2nd Ed. 395-396.

Examples
--------

	. ^gwhet y, index(x)^
	. ^gwhet y, i(x)^


Also see
--------

 Manual:  ^[R] egen^
On-line:  help for @egen@


Author
------

	Gregorio Impavido
	DECVP
	The World Bank
	Washington, DC
	Gimpavido@@worldbank.org



