From a very interesting blog post on web metrics by Avinash Kaushik: 

A very simple test can allow you to figure out if the metric you are dutifully reporting (or absolutely in love with) is gold or mud.

It is called the Three Layers of So What test. 

Ask every web metric you report the question "so what" three times.

Each question provides an answer that in turn raises another question (a "so what" again). If at the third "so what" you don't get a recommendation for an action you should take, you have the wrong metric. Kill it.

This brutal recommendation is to force you to confront this reality: If you can't take action, some action (any action!), based on your analysis, why are you reporting data?

The purpose of the "so what" test is to undo the clutter in your life and allow you to focus on only the metrics that will help you take action. 

All other metrics, those that fall into the nice to know or the highly recommended or the I don't know why I am reporting this but it sounds important camp need to be sent to the farm to live our the rest of their lives!

Source: www.kaushik.net