This metric, as I discuss in Chapter 14, can be the single most important number in determining your split test winners for ads and landing pages.

Note: This calculation is valid only under two conditions:

1. you have chosen "rotate my ads evenly" in your campaign settings
2. your ads generate identical quality scores for your keywords

If either of these conditions doesn’t apply, then you’re comparing apples to adjustable seat posts and you’ll get useless and misleading data.