Advertisers may get easily confused between Quality Based Pricing and Quality Index Score, thanks to their similar-sounding names and also for a fact, they have a similar concept, however they are absolutely different and it is easy to demarcate between the two based on Michael Mattis's explanation.
Ă˘â‚¬Ĺ“Quality-Based Pricing: The Ă˘â‚¬Ĺ“qualityĂ˘â‚¬Âť in Ă˘â‚¬Ĺ“quality-based pricingĂ˘â‚¬Âť refers to the quality of traffic you receive from our partners and publishers. Depending on the relative performance (conversion rate and other factors) of the traffic from the partner or publisher site where the click came from, the cost of your click may be discounted. In a nutshell, quality-based pricing has nothing to do with your position in search rankings.
Quality Index Score: Your quality index score, on the other hand, reflects the performance (including click-through rate and other measures) of your ads, which does impact your position in search rankings.
With quality-based pricing, there is no action that advertisers need to take. ItĂ˘â‚¬â„˘s the responsibility of the partners or publishers (the ones displaying your ads) to help us provide you with quality traffic.Ă˘â‚¬Âť