Earl Babbie, The Practice of Social Research, 5th ed. (Belmont, CA: Wadsworth Pub. Co., 1989), Chapter 7.
Content Analysis is a technique by which objective, statistical methods may be applied to documents (which may include media such as television show tapes, as well as written documents) to determine the attitudes, assumptions, or biases of the producers and, more indirectly, the intended readers or viewers of those documents. For example, we may examine political speeches to find what sorts of buzz words politicians of various stripes use: "freedom," "enterprise," "equality," "fairness," "opportunity," and so forth. We may examine network prime time television shows to find out how much on camera time is given to men, to women, to the young, to the old, to whites, to blacks. In more complex research designs, we may search for features that are subtler than simple word uses or on camera appearances for example, the appearance of themes such as equality of opportunity in political speeches, or the prevalence of violence on television shows.
Content analysis, then, is a way of passing that which seems purely subjective the intent and biases of the creators of documents under the objective lens of our analytical microscope. However, the objectivity of the result of a content analysis study depends in large measure on the degree to which the documents we look at, and the materials within those documents, accurately mirror the universe which we are attempting to study. For example, suppose we wished to survey the public agenda of top American political leaders in recent decades, and decided to do so by performing a content analysis of Presidents' State of the Union messages. The result of that study would have a thoroughly Republican and conservative orientation, because every State of the Union message since 1969, save for Jimmy Carter's four, has been delivered by a conservative Republican...