Conversion rate optmization
Too often conversion rate optimization is looked as an independent measurment of success, rather than the rate it expresses. Put simply, a conversion rate is the number of succesful conversions divided by the number of opportunities. The rate chages as a result of changes to these two numbers, rather than independently.
The easiest way to change the rate is to reduce the number of missed opportunities, i.e. the denominator, but cutting out the bad traffic. This could lead to cutting bad ad spend, blocking bot traffic, etc. The ideal way to change the rate is by increasing the number of conversions, i.e. the numerator, by convincing more visitors to sign up, buy, covert, etc.
Of course, the two nubmers rarely improve at the same time and there are flucatations along the way. It's a rate best compared against its own historical performance via well structured analytics goals.
There's no single solution to converstion rate optimziation. It's a process of asking the right questions, looking at the biggest problems and opportunities, and properly testing hythotheses for improvements.