Adwords optimizing

Advertisers should test multiple ads to fine-tune campaigns and find out what is
effective. For this purpose, AdWords offers optimized ad serving. This means advertisers
can circulate multiple ads at once and Google will automatically start to circulate
“better-performing”ads more frequently. In this approach, AdWords optimizes
performance automatically, based on a performance algorithm developed by Google.
The problem with optimized ad serving is that it is not sufficiently sensitive to random
variation. In other words, one ad can often get ahead completely by chance.
Such an ad will appear more frequently than the others and this can skew performance
data. It is possible to have ads with identical ad copy circulating at different
rates because one was “outperforming” the other!
In general, avoid circulating better-performing ads more frequently, especially in the
middle of an experiment. To optimize your ad group, you want to decide which ad
has the better CTR as soon as possible and circulate that ad 100% of the time.