I have an experiment that consist in two stages and 24 subjects between three groups.
On the first stage, subjects were managed for them to answer in a certain way given the group (growth curve model).
On the second stage, once our subjects had already learnt I want to test a different factor (Context) between groups. For that, I have a cross over design 2x2. The subjects where assigned to sequences of "treatment" (Context A and B) with 2 periods.
Since the first stage is a forerunner, I would like to add the last session of the first stage as a baseline. However I am having trouble with understanding how to do it.
My approach was to code the baseline as a level of Context, and at the Period factor set 0 as baseline.
The data is like this:
A7 is the baseline measurement.
I run the next model that gave me a really nice adjust $R^2=0.88$
I´m new in this kind of designs, so I not sure if my model is valid.
I know that in the way I define my model I have problems with interactions since Period 0 just have "Context"=baseline, and in Periods 1 and 2 just have levels of Context A and B. But I´m just interested in making planned comparisons.
Is it correct to add baseline in this way?
Could you lead me a little bit about the subject.