3 main questions are usually addressed in the introduction: What is the major theory that frames the work being done? What research question is under investigation? What specific hypothesis (or hypotheses) is being tested?

To understand how these questions relate to each other, let's look at a classic diagram describing the production of scientific knowledge.

Two processes are depicted in this diagram:

Most biological studies investigate a particular research question that arises within a major theoretical framework. In such studies, theory and evidence working in close association. To better understand this, let's consider the research question:

Are athletics detrimental or beneficial?

In the late 1800's and early 1900's, many people began participating in competitive athletics, including team sports and racing. Many scientists and physicians felt that while moderate exercise was beneficial, the intense exercise of athletics was detrimental to human health. Many specific facts supported this view. For example, it was observed that athletes had "swollen" hearts. There were even recorded incidences of athletes dying while in competition. Thus, a theory that intense exercise was detrimental began to develop.

Theoretical frameworks allow scientists to develop specific research questions that investigate the effects of exercise. For example, the mechanism of the development of an enlarged heart in athletes might be explored. The results of these studies will contribute to the cumulative evidence and may lead scientists to modify or even overturn the major theory.