My question is regarding the second step of the assigment. We are suppose to include intervention status as a between subject factor. When I compared this assigment with the example discussed in the classroom I noticed that when we examined gender and time we included both in the box for within-subject factor and then we examined as many groups as combinations were possible with this two variables (e.g. pre-females, pre-males, post-females, post-males, etc.). Putting the newgrp under between subject factor do NOT allow us to have as many groups as possible combinations of the variable (Prep Time 1, Prep Time 2, No-Prep Time 1, No-Prep Time 2). It also happens that just Time is analized in the Mauchly's Test of Sphericity and in Tests of Within-Subjects Contrasts the group intervention is not analyzed, just Time and the Interaction between Time and newgrp is included. Is that how it is supposed to be? If yes, why is different from the example discussed in class? Do we need to create the groups as computing a new variable?
posted by Anonymous @ 8:33 PM
2 Comments:
At 10:20 PM,
Unknown said…
For Mauchly's test - only within-subjects variables (or interactions that involve them) are listed because sphericity is only an assumption for repeated measures IVs - not for the between-subjects variables. If you are talking about the example in the mixed design lecture - it's not different. Slide 10 shows that only time was included in Mauchly's for the example in class.
In terms of having as many groups as possible to compare - are you thinking of the post hocs? The comparisons on slide 12? You do not need to compute a new variable for your between subjects variable, but you may need to do a post hoc.
At 6:48 AM,
Mari said…
This is actually the same question, at heart, as Karlin's question below.
In an attempt to give you an easier model to analyze, I left gender out of the design you have, and you were only working with the husbands' data.
Without gender, there is only one repeated measures factor, so as Kelly noted, it is completely appropriate that there be fewer Mauchly tests and fewer entries in the within subjects table.
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