it can and also cant be, if you're bias you strong strong favoritism. like if I was supposed to do a piece on the election, and im a republican if all I did was talk about how great trump is over Hilary (I don't like either actually) that would be a biased piece, depending on what type of piece the need you can really use a bias or an un biased opinion. For the best piece id go for unbiased unless you want to put yourself in there.