In order to study the effect of television on an audience, a student watches old tv shows and compares them to new ones. this is an example of:

   Content analysis

Explanation:  It is a method for analysing different formats such as text, audio or in this case video (television), therefore, the media. So it examines, researches, analyses content on a number of aspects. There is no focus on the impression of some text or video content, which is actually an evaluation. The focus here is on exploring which phrases or words are used, which depends on the time, therefore in the spirit of the times, so as such it is variable after a number of years. That is why students who do this kind of content analysis review and compare old TV shows with today's ones. It means summarising what patterns of communication are present, that is, words, phrases, topics, and how much their representation is in communication, that is, researching the quantity of those words and phrases.