Professor Tim Groseclose of UCLA has recently published a book, Left Turn: How Liberal Media Bias Distorts the American Mind. He uses clearly defined quantitative measures to evaluate the bias of media outlets.
In Left Turn, he scientifically measures the political content of media outlets and converts that content into a “Slant Quotient” of the outlet. To measure the bias, he compares “Slant Quotients” of news outlets to the “Political Quotients” of the typical American voter and political leaders.
Groseclose concludes that the great majority of all national media outlets have a liberal bias. He also points out the conservative bias of a very few outlets. But he determined their conservative bias is less than the liberal bias of most national media.
Dr. Groseclose also cites evidence that the media has shifted the political views of Americans and caused them to be more liberal. So media bias is both real and unfortunate.