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In this experiment I'm trying to make, one group of people watches a lecture series and one does not. Before the lecture series, both groups' levels of optimism, knowledge, and anxiety are assessed. After the one group watches the lecture series, both groups are again assessed with the same dependent variables. I want to determine if there is a significant difference between the changes in the before and afters of both groups.

I tried to run a 2-way repeated measures ANOVA to compare the changes in the control vs experimental group, but I can only input one dependent variable at a time. I tried to use a MANOVA as well but I didn't get that to work either.

The only thing I can think of is running a 2-way MANOVA where my independent variables are watching/not watching the lecture series and time, but I cannot add levels like I can with a repeated measures ANOVA. The simpelst thing I can think of is to run three separate 2-way repeated measures ANOVAs or just three separate paired-sample t tests, but it doesn't answer what I want it to answer.

Any help would be greatly appreciated!

kjetil b halvorsen
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jl99
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    Would it not be more straightforward to calculate the difference for all individuals and then compare the mean difference for both groups using an independent samples t-test? – Maarten Punt May 05 '20 at 14:59
  • @MaartenPunt that makes a lot more sense I think. Thanks, I figured the answer was more straightforward than I thought – jl99 May 05 '20 at 15:03
  • See https://stats.stackexchange.com/questions/3466/best-practice-when-analysing-pre-post-treatment-control-designs – kjetil b halvorsen May 05 '20 at 16:10
  • Similar to [this Q&A](https://stats.stackexchange.com/questions/463172/statistical-tests-when-sample-size-is-1/463198#463198). You'd have Lectures Y/N and Before/After instead of 3 Methods. There's nothing 'wrong' with comparing D = After-Before for two groups, but the 2-way ANOVA might show more. (What if Before scores were much lower for one group than for the other? You might not notice that just looking at differences.) – BruceET May 05 '20 at 21:12
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    @kjetilbhalvorsen thank you – jl99 May 06 '20 at 04:25
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    @BruceET thank you very much! – jl99 May 06 '20 at 04:26

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