Does the actual ad CTR effect Quality Score?

I was just told by tech support that it doesn't...

[wedouglas]

I was told that the CTR on ads was just used to help decide which ads work better for you.

Am I being misled or does the ad really have very liitle effect on your quality score other than the text it includes?

[idolw]

[google.com...]
it is written:

Quality Score: Quality Score is the basis for measuring the quality of your keyword and determining your minimum bid. Quality Score is determined by your keyword's clickthrough rate (CTR), relevance of your ad text, historical keyword performance, and other relevancy factors. The higher your Quality Score, the lower your minimum bid and price you'll pay per click.