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SPSS Topics Discussion > Three condition within subject design study

Hi,
I am wondering if you could help me with my analyses for a within-subject design crossover trial I recently conducted. The design is as follows:
Each participant completed three conditions (randomly assigned to condition order) on three separate days. Measures were taken seven times during each condition. I want to determine whether there were statistically significant differences between the conditions in a dependent variable (DV) at each of the seven time points. The DV is a continuous variable.
I have conducted a two way repeated measures ANOVA (Analyze - General Linear Model - Repeated Measures in SPSS) with Time (7) and Condition (3) as the within-subject variables, and under the options menu, I ticked ‘compare main effects’ and selected Bonferroni for the CI adjustment. The output from this provides the main effect for Time, Condition, and the interaction effect Time*Condition. It also produces 2 tables of Pairwise comparisons, showing the mean difference ( and SE) in the DV between conditions, and the mean difference ( and SE) in the DV between time points (with associated p-values). It also produces a table for the Time*Condition interaction, with the mean, SE, and CI for each treatment at each time point. But it does not compare the three conditions at each time point! I realize I could conduct t-tests (or similar) at each time point, but I'm worried about the risk of a Type 1 error.
Is it possible to compare the mean difference between conditions at each time point? And if so could you please explain how to do this?
I hope that makes sense. I've been struggling with this for a while, so would really appreciate some help!
Kind regards,
George

May 7, 2012 | Unregistered CommenterGeorge

Also, if possible, I would really appreciate it if you could tell me how to enter baseline as a covariate when there are three baseline variables for the DV, one for each condition.
Thanks,
George

May 9, 2012 | Unregistered CommenterGeorge

George,

the model you are trying to examine is fairly complex, but if you'd like to send me your output file, so I can see more clearly what you have (and what you don't, that you are looking for), I'll be happy to try to provide an idea about how you can obtain the comparison you seek. If you'd like to do this, you can send the file to: statsmakemecryguy@me.com

May 16, 2012 | Registered CommenterJeremy Taylor