7 Google Quality Score PPC Myths
Quality score is actually calculated at three different levels. These are: the account level, the ad level and the keyword level. It’s useful to note Google’s new way of describing this now, which is “the CTR on the keyword and the matched ad”.
So, it’s actually now a combination of the keyword level and the specific ad we are considering showing. All this says to me is that the keyword CTR is still paramount. A secondary concern is that changing ads will “reset” Quality Score to the default. And a minor factor is account wide Quality Score.
(Source: searchengineland.com)
