RE: st: question on chow test

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 11:07 PM 2/19/2005 -0800, Daniel Schneider wrote:
> But how can I test if, for example, the subgroup of x1 is differing
> across groups. Is
>
> testparm g2x1 g3x1 g4x1
>
> Is this the correct way to do the test?
If the test statistic is insignificant, then that means that the effect of 
x1 does not significantly differ across groups.


> Secondly, can I use the differences between
>
> g2x1 <-> g3x1 <-> g4x1
>
> to describe the "strength" of the differences (amount of difference, in
> the same meaning as effect strength compared to statistical
> significance)?
I am not totally sure I follow you, but a command like

testparm g2x1 g3x1 g4x1, equal

would test whether the effects of x1 are the same in groups 2, 3, and 4.

There are potentially zillions of tests you can be doing here, so you want 
to be careful you aren't just capitalizing on chance.

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