Let's say I have a range of formulations, and each formulation contains a different starting rate of water "x", and I want to test how fast the formula dries out over time (ie. loss of water over time), and put this on a plot. Let's suppose the starting rate of x for each formulation is known, but there is no control for over the starting rate of x. In order to make the regression on the plot between each formulation more comparable, is it appropriate to scale x for each formula to be the same starting rate?
For instance: x1: 20, x2: 35, x3: 22
And then, to scale each resulting regression I could just adjust each data point by ~57% for x2, and ~91% for x3; so that they all have a starting rate of x = 20 and scale the remainder of the data points by those same percentages for x2 and x3?
Thank you!