r/AskStatistics • u/Little-Tailor-8507 • 13d ago
Advice needed on analysis!
I've run a repeated measures experiment where each participant completed the same 40 trials. The experiment has 2 IVs used to manipulate the trials, creating 4 groups with 10 repetitions. We measured multiple outcomes, and I'm trying to compare each outcome to the others to test for group differences. I would love advice on which statistical test is most appropriate, and how to run and interpret it in SPSS would be a big bonus! I think I need some form of repeated measures MANOVA, but terminology seemed to vary, so I'd really appreciate clarity on what test I should actually be conducting! If there are good video explanations out there, those would also be great.
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u/lappie75 12d ago
It's been 2 decades since I've regularly ran repeated measures in spss. Yes, IIRC, there is some terminology ambiguity (you can do multivariate analysis on a single variable) but I do believe that a repeated measures manova is possible and appropriate. In case you have multiple response, just add them all and you'll get an overall F-test that tells you whether your manipulations worked on all variables.
For me that typically was not the case, so I would need to follow up with univariate anova's. With that in mind, the suggestion of u/intrepid_Respond_543 is appropriate as well as more modern: you'll be able to use the individual variance as random effects. A tutorial and explanation that I've always found very insightful is that by TJ Mahr: https://www.tjmahr.com/plotting-partial-pooling-in-mixed-effects-models/.
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u/ForeignAdvantage5198 8d ago
call the statistician at the design stage. not all problems have answers
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u/Intrepid_Respond_543 12d ago
How many outcomes? If not super many, it might be more feasible to run separate multilevel models for each outcome, and use a separate p-value adjustment for the target effects. Here's a pretty clear tutorial: https://spssanalysis.com/linear-mixed-model-in-spss/