Should I Turn Off Low Position Keywords?
We all know CTR goes down with average position. Let's say the ROI isn't high enough to justify bids high enough to get you in the top 5 ot 6 positions. Is it best to pause the keywords or just live with the ads appearing on the side near the bottom of the page?
On one hand, you still a chance (although small) of getting clicks that lead to conversions. On the other hand, if you have a lot of keywords appearing in low CTR positions, that's going to bring your average CTR down and Google is going to prefer to show ads with higher CTR.
Does CTR effect add placement only indirectly by it's effect on Quality Score and if so, I would assume (or at least hope) that Google QS formula uses an "position adjusted" CTR rank relative to other competitors who have advertised in the same position. So although showing your add at position 6 is going to have a low CTR and bring your average CTR down, if it is above the average CTR of other advertisers advertising at 6, then it should IMPROVE QS not decrease it, right?
Re: Should I Turn Off Low Position Keywords?
Yes, QS is "position adjusted". Some keywords will work better for you in lower positions on the page. If that's what your data says, sounds like a good idea.
Yes, CTR indirectly affects QS, but it is still the main factor of QS.
Average CTR and QS across your account still affects the general auction, even though you will see 6/10 for new keywords That don't have enough impressions to get their own score. It seems your impression count will be low on these keywords compared to other keywords in your account, so I would think the impact to be minimal in keeping keywords that are marginally profitable.
Bottom line for me is, if the keyword converts profitable in any position or under any bidding strategy, keep using the keyword.
Best of Luck!