I've never had to test for an "ordered continuum" between groups, so
maybe others will chime in. Perhaps you could do the conjunction of the
regions that satisfy 1 > 2, 2 > 3, and 3 > 4 ?
good luck,
-MH
On Fri, 2012-01-06 at 12:34 +0000, Cagri Yuksel wrote:
> Thank you Michael, that was enlightening. The answer is no, we can not assume that there is a linear relationship between these diagnostic groups.
>
> So how should a model be testing a continuum of GM abnormalities between these 4 diagnostic groups using a multiple regression model ? I really can not think of anything at this point.
>
> Cheers
>
> Cagri
>
> On Thu, 5 Jan 2012 10:56:47 -0600, Michael Harms <[log in to unmask]> wrote:
>
> >Whether or not a linear model relating the groups makes sense depends on
> >on the specific groups, so I don't know whether it makes sense in your
> >context or not. I'll just note that modeling a linear relationship
> >between groups is a specific hypothesis that assumes that each step up
> >in the "group" variable yields an identical change in the dependent
> >variable (since all the groups were themselves spaced by a delta of 1
> >unit). This is *not* the same as hypothesizing that there is merely a
> >continuum in the DV such that 1 > 2 > 3 > 4 (or 1 < 2 < 3 < 4).
> >
> >cheers,
> >-MH
> >
> >On Thu, 2012-01-05 at 16:38 +0000, Cagri Yuksel wrote:
> >> Hello Michael,
> >>
> >> Thank you for your answer. Yes, I realized my mistake about the interpretation of the results right after I sent the message.
> >>
> >> These diagnostic groups are related and this analysis is to test an a priori hypothesis about a possible continuum of GM abnormalities in these groups, that's why I was thinking a linear model.
> >>
> >> Do you think it makes sense ? Do you have other suggestions?
> >>
> >> Thank you again,
> >>
> >> Cagri
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