In A/B testing, is CTR the only relevant figure?

[ChanandlerBong]

I'm doing some split testing based on colors, fonts, font size, even placement. Both ads have space for 4 ads and are equal in dimension.

the problem is that though the two ads are pretty close when it comes to CTR, the different CPC is making one of them come out on top for CPM/earnings.

I should only look at CPC, shouldn't I? I mean, if one ad has red links and another has blue links, that won't change which 4 ads win the auction, so anything beyond CTR is statistical clutter, isn't it?

[DaStarBuG]

If you are testing link color, font size, fonts or placements which only affect CTR then CTR should be your messure.

If you compare Ad Size or Image vs. Text Ads then eCPM/RPM should be your messure.

For example I did a split test with image vs text on one ad spot:

Each Ad Unit got around 40k Impressions
Image & Text: CTR ~0,9 | CPC ~34 Cent | RPM ~2,9 EURO
Text only: CTR ~0,3 | CPC ~17 Cent | RPM ~0,44 EURO
Image only: CTR ~1,0 | CPC ~31 Cent | RPM ~3,2 EURO

Even though CPC for Image&Text is higher I earn more money when I display Image only Ads.

Hope this helps