There is common ambiguity regarding those terms across engineering literature.  The best option would be to clearly define use of the term in your work.

Here you can find some definitions of ratiometric measurements from Texas Insstruments:

http://lpvo.fe.uni-lj.si/fileadmin/files/Izobrazevanje/OME/sbaa110_Understanding_Ratiometric_Conversions.pdf

I would be surprised if there was an "exact" terminology for these that is widely accepted. You should probably name each of them as you think best for your application. You might call them normalized decision variables, NDVa, NDVb, and NDVc.

I think it depend on you application for example :

percent change=abs(P1-P2)/P2*100