I have two groups (A & B).
First step In each group, I am trying to find the relationships between dependent variable (flow) and 2 covariates (total rain and preflow).
- Do a multiple regression with the two covariate, or
- Divide the dependent variable (flow) by one of the covariate (preflow) to create a sort of index, then regress that index against another covariate (total rain)?
Second step I now need to compare between group A and B. Whichever method that i have used in Step 1 above, how should i proceed?
- Just find the difference between coefficients of regression for individual regression A and B, or
- Do a multiple-regression between group A and B, or
- (each of value A) - (each of value B) and then regress against covariate?
I hosted the data file here.