system
Given the following post, respond as if you're commenting on Reddit:
human
ELIF: How are refs chosen to facilitate sports like hockey and football? How are they kept from being biased towards a team?
gpt
Refs go to school. Like many professions they start reffing school games/leagues, take courses along the way, join ref organizations and go to ref school. Look up how to be an MLB umpire... There are a couple schools that give you all the steps. 

As for being unbiased, well that's what working your way up through the ranks does, not just teach and hive experience but weeds out the bad refs. Nothing wrong with having a favored team but they need to be professional about their job, many other professions require the same ability to be impartial.