http://spssx-discussion.165.s1.nabble.com/Planned-Contrast-Coding-Question-tp5729543p5729545.html
Yes, your proposed contrast does test the interaction of the
linear trend for the two conditions. This should be tested, I think,
after a test that takes out the influence of the overall linear term.
Even if the design is balanced, this reduces the error term. If the
design is not balanced, you will be testing the wrong thing.
There should also be a test for the residual (non-linear) interaction
terms, to confirm the linearity.
And the "No FW" condition is, indeed, problematic. As you
look at the matrix of contrasts, you can see that the means for
"hybrid" are treated exactly the same as the means for "No FW".
Thus, the increase in the error term is the way that Hybrid has its
influence on the test of hypothesis - and NoFw has exactly the same
influence. If that is not acceptable, you need to drop the NoFw subjects
from the ANOVA.
--
Rich Ulrich
Date: Fri, 8 May 2015 14:18:13 +0000
From:
[hidden email]Subject: Planned Contrast Coding Question
To:
[hidden email]
All
I have a question regarding
a study utilizing the below 2 x 4 between-subjects design.
|
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Variable Y
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Variable X
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Y1
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Y2
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Y3
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Y4
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X1
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A
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B
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C
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D
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X2
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E
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F
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G
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H
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In order to respond to a reviewer’s concern, we need to test the following ordered interaction:
Participants in condition Y4 are less likely than those in condition Y3 who are less likely than those in condition Y2 to engage in an action and this effect is greater under X2 than X1.
[(B > C > D) < (F > G > H)
We currently are using the following contrast coding to test for this planned contrast, but I just don’t know if it’s correct given that we want to ignore the No FW (Y1) condition.
/lmatrix 'why less likely than hybrid which is less likely than pro/con to allow aggressive reporting and this effect is greater under less precise standards' standard*framework 0 1 0 -1 0 -1 0 1
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No FW
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Pro/Con
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Hybrid
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Why
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More precise
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0
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1
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0
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-1
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0
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Less precise
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0
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-1
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0
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1
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0
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|
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0
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0
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0
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0
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Any help is much appreciated.
Tony
A J Baglioni jr
Associate Professor
McIntire School of Commerce
343 Rouss/Robertson Hall
University of Virginia
434.924.4961
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