Bad data takes you confidently in the wrong direction

And not just bad as in low-quality, or unclean, or full of errors (though all that is obviously bad).

Bad as in the wrong data to even be looking at.

One thing we've learned from Kahneman, Tversky, Cialdini, and others, is that what we pay attention to shapes our reality. 

A realtor drives through a neighborhood and only sees home values. A pickpocket stands in a crowd of Nobel laureates and only sees pockets. 

The same is true in marketing. Looking at the wrong data takes you in the wrong direction — but confidently. 

And unfortunately many of us are paying attention to things because they're easy to measure, not because they're important to.