Content analysis is a widely used technique in communication sciences. It is a method by which some observable contents, such as texts, images, objects, etc. are transferred through coding into a measurable and verifiable form. The process of conducting a content analysis follows the general research process of quantitative inquiries. Perhaps the most distinctive part is the construction of a coding scheme, a detailed instruction for identifying and classifying the units of analysis.
The unit of analysis refers to what is counted, what is the “analytical whole” taken as a separate unit. Originally, content analysis was introduced to the communication sciences to bring analytical rigor and objectivity. Therefore, the “content” was originally defined as manifest, i.e. observable and as unambiguously counted as possible. Examples of such units are the lengths of newspaper articles as measured in inches or the numbers of different sexes in different scenes of a soap opera. Content can also be visual, non-verbal or even audible. Manifest content is easy to determine beforehand and to identify from the data. (Units of analysis can be less manifest though, i.e. based on the subjective interpretation of the coder. An example of such unit of analysis could be attractiveness or an emotional tone of voice, positivity or negativity of a speech act, etc.)
The identification of contents can be subject to the subjective biases of the coder. More objectivity can be brought to the analysis by using more than one coder and calculating an inter-coder coefficient. In this way, the reproducibility of the results by other researchers can be used as a measure of reliability. There are many ways to do the calculation, and the whole data does not need to be double-coded, but a fraction of it, such as 10–20%. One of the most-used reliability measures in this context is Cohen’s Kappa.