CTR vs IUC - ad testing

[Jimb0]

I've been having a debate with a few people about the appropriate measurement for finding a winning ad. I think it should be IUC or Impressions Under Conversions where you run an AB split test and compare conversions with how many impressions the 2 ads have and run your statistical analysis. I hear others telling me to measure CTR. The problem with CTR is that you can have 2 ads with 1000 impressions each ad A has 500 clicks and zero conversions and ad B has 250 clicks with 100 conversions. Clearly ad B is the winner but it is the loser when you measure by CTR. How do you optimize towards conversions without sacrificing CTR?

Any thoughts would be appreciated.

thank you.

[eWhisper]

I'm a huge fan of per impression metrics such as:
Profit per impression
Conversion per impression
Revenue per impression
etc - based upon account goals

Per impression metrics take into account CTR, Conversion rate, and potentially revenue all at the same time.

Here's a long post I wrote 8 years ago that is still very relevant to this topic on impression testing: [webmasterworld.com...]