Mindvalley labs had a couple good posts on this topic a few months back (this one and this one). Both illustrate that keywords in your ad copy (whether it’s a sponsored ad in the paid results or your title & meta description in the organic results) don’t just affect whether people click through to your site more often – they actually influence the degree to which those visitors take action.
That’s a pretty remarkable discovery, and it suggests that if you’ve been concentrating solely on CTR as the metric for your web-based ads, you might be losing out. Make sure that as you test copy, you watch not only CTR, but conversion rates as well. You never know when an ad might send you less traffic, but more conversions.