Google Adwords SUPER Tip #8...
TURN OFF 'Automatically Optimize Ad Serving' WHILE TESTING
Google allows you to rotate ads evenly to split test one against the other. They even offer to automatically optimize them by serving up your best performing ads more frequently.
When you're testing 3 or more ads, and want to identify the best performer, you want to turn OFF the automatic ad optimizer so each version of your ad is displayed evenly.
It's how I was able to isolate this winning ad, which pulled 0.4% CTR -
... from it's competitors like this one below which pulled 0.2% CTR
Turn Your Ordinary Business Into A Cash-Flow,