Thinking of getting fancy with Quality Score? It may be better to be more straightforward. Read on.
Quality Score is the driving force in the PPC ranking algorithm at all major search engines; indeed, it has been since Google AdWords Select was released in 2002. You could do far worse than to model your strategy as if Quality Score were essentially unchanged from that early formulation of AdRank = CTR X Max Bid. Alterations to the formula have largely constituted refinements intended to make Quality Score more accurate, less clunky, and more appropriate to each specific user query.