I know programmers don't like to hear about intuition and that is why I am probably being down voted for this too.

But that is what makes what you do stand out and what separates the excellent designer from the mediocre designer.

Just the same that makes the excellent developer stand out, that which cannot be put into a data set.

I challenge anyone to find a common design functionality that couldn't be solved with common sense and intuition.

Something that you could prove the actual results would be better if they where based on data.

The problem of course is that no such data exist.