I need to perform the ANCOVA for a repeated-measures design.
I tried to adapt the Julian's ANCOVA procedure showed on the https://www.youtube.com/watch?v=mApbp1RDy-U to my study case (repeated-measures design). Initially, I did the following actions:
1. In the Fit Y by X dialogue: I selected VAR_Y as "Y, Response" and VAR_X as "X, Factor";
2. For "Group by" I selected the variable Timepoint;
3. Density Ellipse: I selected .50;
4. Then I clicked on "Fit Line".
JMP plotted a line for each timepoint and some of them crossed other lines. So, the parallel slope assumption did not met. So, how can I handle with it and perform the ANCOVA?