I have two (Test and Control) groups of data. Data in each group is divided into 10 (ordinal) period. In each of these periods, number of observation ranges anywhere from 22-53. The assumption is that values (coefficient of slope, intercept, mean) will decrease when going from Period 1 to Period 10. What is the best test for this?
- Within each group, fit a linear model and extract coefficients for each period. Regress the coefficients against period 1-10. Run ANCOVA.
- Same as above, but Run Wilcoxon test instead.
- Within each period, compute the difference between test group and control group, then fit a linear model against period (1-10).
- Any other better ways?