A bias is a prejudice in a general or specific sense, usually in the sense for having a preference to one particular point of view or ideological perspective. However, one is generally only said to be biased if one's powers of judgment are influenced by the biases one holds, to the extent that one's views could not be taken as being neutral or objective, but instead as subjective. A bias could, for example, lead one to accept or deny the truth of a claim, not on the basis of the strength of the arguments in support of the claim themselves, but because of the extent of the claim's correspondence with one's own preconceived ideas.
A systematic bias is a bias resulting from a flaw integral to the system within which the bias arises (for example, an incorrectly calibrated thermostat may consistently read – that is 'be biased' – several degrees hotter or colder than actual temperature). As a consequence, systematic bias commonly leads to systematic errors, as opposed to random errors, which tend to cancel one another out.
In practice, accusations of bias often result from unacknowledged favouritism on the part of a critic or judge, or indeed any person in a position requiring the careful and disinterested exercise of arbitration or assessment. Any tendency to favour a certain set of values naturally leads to an uneven dispensation of judgment. It may also be noted that, if a person were to take their own preexisting view as a priori balanced without acknowledging their own personal inclinations, any person or organization that disagrees with their views is likely to be viewed as biased regardless of that person or organization's actual efforts at balance. It may be observed that bias is, in a sense, reflexive, unacknowledged or unrecognised bias potentially leading to its apprehension (with or without good reason) in others.
This is particularly common in discussion of news media outlets such as CNN, Fox News Channel, The New York Times, Al Jazeera, and so on. For example, Bill O'Reilly has made accusations of liberal bias against the staunchly conservative Globe and Mail; at the same time, critics of O'Reilly accuse him of a conservative bias. Control Room, a documentary film made in 2004, has examined the role of bias in the media, through an examination of the conflicting methods of reporting the events of the U.S.-led invasion of Iraq in 2003, in Western and Arabian news networks.
