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Date: Thu, 18 Nov 1999 14:04:21 +0100 (MET)
From: Jean-Baptiste POLINE <poline@uriens>
Subject: Re: F-contrasts
To: [log in to unmask]
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dear Michael
>
> what is the theoretical and practical difference between
> the "effects of interest" F-contrast in the form
> [ 1 0 0, 0 1 0, 0 0 1] and a single F-contrast entered as
> [ 1 1 1 ] ?
There is an important (theoretical and practical) difference :
in the first case, you are testing whether the three first
regressors "explain" something of the data, in the second
you are testing whether the sum of the parameter estimates
corresponding to these regressors is "too big" (positive or
negative).
There was a similar question sometimes ago on the list,
may be you could search for F-contrast on the list archive.
best,
JB
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