Could someone tell me how can I write to the group from my mail and
recive your mails?
I'm trying to participate on the list but I don't know how is it.
Thanks a lot list.
Regards
Ignacio
--- In [email protected], Richard Williams
<Richard.A.Williams.5@n...> wrote:
> At 10:35 PM 1/18/2004 -0500, Michel Camus wrote:
> >In fact, they do provide the same results.
> >I am not a statistician, but using the robust option with regress,
as
> >suggested by Christopher Baum, gave me the same result as teh
ttest with
> >unequal variance after subtracting the hypothesized difference.
> >I do not know why you obtain different results" Do you actually
have two
> >groups with different variances in you simulated example, Richard?
> >See my response (in 5 minutes from now... to Karen, simulating
data
> >similar to hers).
>
> In the various little experiments i have done, the differences
between
> regression with robust standard errors and the t-test with unequal
> variances have been very small. My guess is the approaches aren't
100%
> equivalent (unlike the t-test with equal variances versus
regression) but
> that it would only make a difference in some incredibly borderline
> situation. On the other hand, I have been surprised before, so it
might
> not hurt to do it both ways.
>
> I like your examples in your later message. In terms of what
should be
> presented in the writeup, however Karen does it, she may just want
to give
> the final test statistic; my guess is the audience won't much care
how she
> computed it. If I did have to explain the nitty-gritty of the
> computations, I suspect t-test routines are familiar to more people
than
> regression with robust standard errors. But, the main thing is to
get the
> answer, and this discussion has come up with some good ways to do
that.
>
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