Should I use a research question, hypothesis, or thesis statement?
The way you present your research problem in your introduction varies depending on the nature of your research paper. A research paper that presents a sustained argument will usually encapsulate this argument in a thesis statement.
A research paper designed to present the results of empirical research tends to present a research question that it seeks to answer. It may also include a hypothesis—a prediction that will be confirmed or disproved by your research.