Does each individual ad determine an individual rank?

[venrooy]

If I have several ads running for one adgroup - Does each individual ad CTR determine the rank of that ad?

eg: I have 2 ads running for my adwords "green widget". When I type in "green widget" I'm noticing that the rank of my ad moves up or down the page depending on which of the ads is shown.

And if that is how it works - is it a good idea to delete the ads with the lowest CTR and replace them?

[ronmcd]

I think it's "quality", not clickthrough. Clickthrough is only part of the quality calculation, relevance of ad copy etc are now as important. Check the help pages in adwords, they explain it.

And yes, I think it is unique for different ads, so the one showing highest probably has a higher quality score.

But its possible you could have an ad google thinks is of lower "quality" (less relevant keywords in copy) but which has a higher clickthrough (attention grabbing copy). It annoys me a little that this ad will be penalised, but there you go.