Posted by
statisticsdoc on
Feb 08, 2007; 6:15pm
URL: http://spssx-discussion.165.s1.nabble.com/repeated-measures-custom-contrasts-for-linear-trends-tp1073671p1073674.html
Paul,
I would second Richard's suggestions about checking for outliers and looking
at the trends in the actual data. The cubic trend is sometimes hard to
visualize. You are looking for a trend that looks like a stretched out S -
something with two inversion points (two places where the line changes
direction), rather than the single inversion point you see in a quadratic
trend (like a U shaped function). One common type of cubic trend involves a
threshold, where Y is low for low values of X, then Y jumps up for moderate
values of X, then Y remains high for high values of X (or vice versa). I am
not sure what practical context you are dealing with, but this type of trend
is pretty common in learning experiments.
HTH,
Stephen Brand
For personalized and professional consultation in statistics and research
design, visit
www.statisticsdoc.com
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]]On Behalf Of
Paul Mcgeoghan
Sent: Monday, February 05, 2007 8:27 AM
To:
[hidden email]
Subject: Re: repeated measures custom contrasts for linear trends
Stephen,
The Tests of Within-Subjects effects Greenhouse-Geisser is significant .040
and Huynh-Feldt is
significant .027 for the MOVES*IAC interaction.
The Tests of Within Subjects Contrasts indicates a significant cubic effect
(.039) for MOVES*IAC.
So yes.
Paul
==================
Paul McGeoghan,
Application support specialist (Statistics and Databases),
University Infrastructure Group (UIG),
Information Services,
Cardiff University.
Tel. 02920 (875035).
>>> "Statisticsdoc" <
[hidden email]> 05/02/2007 13:17:56 >>>
Paul,
Do you have a significant interaction between MOVES and IAC (i.e., is there
evidence that the slope of the within-subject factor varies as a function of
the between-subject factor)?
Best,
Stephen Brand
For personalized and professional consultation in statistics and research
design, visit
www.statisticsdoc.com
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]]On Behalf Of
Paul Mcgeoghan
Sent: Monday, February 05, 2007 6:02 AM
To:
[hidden email]
Subject: repeated measures custom contrasts for linear trends
Hi,
I have a customer with a within-subject factor (MOVES) with 10 levels and a
between subject factor
with 3 levels (IAC).
He wants to test if there is a linear trend at each of the 3 between subject
factor levels.
What would be the syntax for this?
I currently have the syntax below:
GLM
moves1 moves2 moves3 moves4 moves5 moves6 moves7 moves8 moves9 moves10 BY
iac
/WSFACTOR = trial 10 Polynomial
/METHOD = SSTYPE(3)
/EMMEANS = TABLES(iac) COMPARE ADJ(BONFERRONI)
/EMMEANS = TABLES(trial) COMPARE ADJ(BONFERRONI)
/EMMEANS = TABLES(iac*trial) COMPARE(iac) ADJ(bonferroni)
/EMMEANS = TABLES(iac*trial) COMPARE(trial) ADJ(bonferroni)
/PRINT = DESCRIPTIVE
/CRITERIA = ALPHA(.05)
/WSDESIGN = trial
/DESIGN = iac .
Thanks,
Paul
==================
Paul McGeoghan,
Application support specialist (Statistics and Databases),
University Infrastructure Group (UIG),
Information Services,
Cardiff University.
Tel. 02920 (875035).