Need help with post hoc testing in repeated measures

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Joined: Tue Dec 31, 2013 3:21 pm

Need help with post hoc testing in repeated measures

Postby price067 » Tue Dec 31, 2013 4:35 pm

I need help with post hoc testing in repeated measures. I have 4 groups of mice.
Grp 1: +prog, +PRM, Grp 2: -prog, +PRM, Grp 3: -prog, -PRM, Grp 4 +prog, -PRM. The outcome is a continuous variable called LVDd. LVDd is measured at times 0 wk, 2 wk and 4 wk. Data is expressed as % change for 2 wk and 4 wk compared to 0 wk.
I need to know the difference between 2 and 4 wk in each group and the difference between groups at 2 and 4 wks. When I set it up I only get overall p values for prog and PRM and the interaction but no post hoc testing. Please help! Please make any directions very simple as I am a novice at SPSS. I have attached pdf images that may help.
T Price
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Re: Need help with post hoc testing in repeated measures

Postby GerineL » Tue Jan 07, 2014 2:54 pm

In the menu where you selected your analysis, you can also click on "contrasts", you see you have several options there. Here you can select one option that will help you (e.g., simple last compares the last to everything else).
there are:
elmert, repeated, and polynomial.

Deviation: Compares the mean of one level to the mean of all levels (grand mean)
Simple: Last: compares all levels to last. first: compares all levels to first.
Difference: Compares level 1 to 2, level 3 with the mean of 1 and 2 etc.
Helmert: Compares level 1 with all later, level 2 with the mean of all later, level 3 etc.
Repeated: Compares level 1 to level 2, level 2 to level 3, 3 to 4 and so on
Polynomial: n/a

Just select 1 (or more) you need to get your comparisons.

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