Everyone has a bias.  A bias is generally understood as a preconceived position on a subject often viewed as unreasoned by others.  The reality is the bias is generally not developed through unreasoned mental programming, but rather built out of causal reasoning.  Our experiences in our own life are the anecdotal evidence for much of the judgements we make during the day.  Sugar flakes will be sweet.  Potato chips will be salty.  Some people’s causal reasoning has them jumping the train tracks and believing that there’s floating spoons on mars.

In projects qualitative risk analysis and reliance on expert judgment can also lead to false conclusions.  A project manager with a short list of failures may believe he can will project success simply by forceful demands.  I’ve also seen PMs who grossly misinterpret the difference between a minor risk and a slightly higher risk.  In this situation they exaggerated the difference to the point where they felt the project was in severe jeopardy.  This lead to more worry and significantly lowered the productivity of the team.  

One way to balance a bias is with quantifiable information.  In the case of the PM who over exaggerated risk we were able to show him that the chances while still higher than the norm he was used to were so unlikely that it was a nearly negligible increase.  Using the hard data was only part of the equation.  Communicating the data in a way that allows the PM to be corrected while still saving face is also important.  Publicly disempowering a PM may create a dramatic situation that functions as a hand grenade to product progress.  Sometimes it makes sense to just leave a Lenore Skenazy quote on their desk and walk away.  “All the worry in the world doesn't prevent death. It prevents life.”