Are you defining "likelihood to purchase" from ad responsiveness? Or is likelihood derived from surveys? Or other?

Likelihood to purchase the brand of interest was measured from Numerator receipt scanning data.  It can also be measured via frequent shopper data and from surveys using a constant sum question. The linkage between a baseline probability to buy the brand and the responsiveness to advertising was discovered when we integrated the math from those two areas of study and created a common system of equations.