Media bias is advocacy journalism gone wild, where one-sided arguments masquerade as objective reporting. It "is rarely expressed through distortion of the facts, but rather through the omission of certain facts that would be inconvenient for the outlook of the person or group reporting." A good example is Paul Krugman's claim, in his New York Times opinion piece, that "Everyone knows that the American right has problems with science that yields conclusions it doesn’t like." This statement completely ignores the much worse "problems" the American left has with science, specifically the climate science which refutes the junk science used by liberals to prop up their global warming theory and their "solution" to the "crisis" (see Kyoto Protocol, carbon credits, etc.).
It manifests distortion of news, commentary, non-fiction articles, textbooks, documentaries, speech codes and the like to favor one side's ideas over another's (see partisanship). Dictatorships and other authoritarian regimes which suppress freedom of the press are notorious for their media bias, particularly when all media are controlled directly by a one-party government.
Most journalism schools in free countries address the issue of eliminating bias, although efforts are rarely successful. The U.S. media is strongly polarized, with multiple outlets have strong liberal and conservative biases, depending on which station (or newspaper) is considered. Overall, however, many, including some academics with scientific backing, maintain that the media has a general liberal bias.
Media bias is the reality that any media outlet, personality, or report, regardless of format, has an agenda. As such the information in the report will be crafted in such a way to have the consumer conclude in a manner that aligns with the bias.
Sources of bias
- Deliberate propaganda: Presenting bias with the intention of benefiting the media establishment.
- Institutional bias: The reporters and editors of a media organization may hold political views, which influence their reporting. Reporting on the Vietnam war has been cited as a notable example of such.
- Sensationalism: Media depends on viewership for financial support from advertisers. Thus stories that have little political value but much entertainment value may receive attention disproportionate to their impact. Scare stories are also an example of sensationalism.
- Omission: The inverse of sensationalism, media may overlook important but boring stories.
- Political correctness or sensitivity: Fearful of appearing racist or discriminatory, media may avoid any stories which reflect negatively on a ethnic, social or religious group, especially if the group is a minority.
- Confirmation bias: a type of selective thinking whereby people tend to report what confirms their beliefs, and to ignore, or undervalue what contradicts their beliefs.
- Audience bias: Readers or viewers tend to read news sources with which they agree. Thus, media must reinforce the existing views of their audience, or risk losing them. This source of bias can also reinforce the effect of a moral panic. In this case, the public may receive a distorted perspective that is a result of their own preferences, because the news media will deliberately deliver news not only suitable and desirable to the general public, but may also incorporate bias that would similarly suit the viewer.
Media literacy is a specific knowledge set that is based on understanding that biases exist, examining those bias and how they affect the presentation of the information, asking your own questions, determining what the facts are and if they are reliable, and drawing your own conclusions.
Defining Agenda and Hidden Agenda
The word agenda simply means a goal or desired outcome. Some people believe agenda automatically has a negative connotation but it does not. There is a distinct difference between agendas and hidden agendas. A hidden agenda is a one the a person or groups try to achieve to benefit themselves at the expensive of others or with the disregard for other often through unscrupulous means. 
Yellow journalism is a type of journalism that presents little or no legitimate well-researched news and instead uses eye-catching headlines to attract more attention.
Sources and Vectors
When reports are created they usually begin with an event, then an original report is written based on the event, and then that main story is shared and populated through many outlets. Examples of starting events are research studies, votes on bills, sporting events, and the like. A source is then the first level of stories or content that are created from those events. Then these original sources are picked up by vectors and shared or modified slightly and then shared.
Types of Bias
A large part of the manufactured class warfare dichotomy between liberal and conservative media bias. Both sides will report the same stories with their respective media bias and subsequently try to force different conclusions on the consumers.
Liberal bias is partisan selection or distortion of information to support liberal policies. This bias can be expressed by professors, public school teachers, College Board exams, reporters, writers, journalists, and any other information sources. Typically purveyors of liberal bias falsely present themselves as being objective. Liberal bias includes techniques such as distorted selection of information, placement bias, photo bias, and liberal style. There is a difference between being liberal, having a liberal perspective, and presenting information with a liberal bias.
Conservative bias is partisan selection or distortion of information to support conservative policies. This bias can be expressed by professors, public school teachers, College Board exams, reporters, writers, journalists, and any other information sources. Typically purveyors of conservative bias falsely present themselves as being objective. Conservative bias includes techniques such as distorted selection of information, placement bias, photo bias, and liberal style. There is a difference between being conservative, having a conservative perspective, and presenting information with a conservative bias.
The Media Research Center Key Findings
"Surveys over the past 25 years have consistently found that journalists are much more liberal than rest of America. The Media Research Center has compiled the relevant data on journalist attitudes, as well as polling showing how the American public’s recognition of the media’s liberal bias has grown over the years."
Journalists Vote for Liberals
Journalists Say They Are Liberal
"Surveys from 1978 to 2005 show that journalists are far more likely to say they are liberal than conservative, and are far more liberal than the public at large."
Journalists Reject Libertarian and Conservative Positions
"None of the surveys have found that news organizations are populated by independent thinkers who mix liberal and conservative positions. Most journalists offer reflexively liberal answers to practically every question a pollster can imagine."
The Public Recognizes the Bias
"Nearly nine out of ten Americans believe journalists sometimes or often let their personal views influence the way they report the news, and most say this bias helps liberals. Even a plurality of Democrats agree the press is liberal."
Denials of Liberal Bias
"Many journalists continue to deny the liberal bias that taints their profession.
Admissions of Liberal Bias
"A number of journalists have admitted that the majority of their brethren approach the news from a liberal angle."
- Nat Brown - National Review
- First They Came For The Climate Scientists
- Jack discusses agendas in a listener email show