There are three assumptions in research: epistemological, ontological, and methodological. Epistemological refers to the ways to acquire the knowledge (Alan Bryman, 2001). The knowledge those are acceptable in certain paradigms. For example, epistemological in the normative paradigm is how the social world can investigate as natural science. Hypotheses have to test by empirical approaches. The results have to be objective through scientific method. In contrast, epistemology in interpretive is acquire the knowledge by investigate the phenomena in many ways, because the social context is different from natural science. Therefore, investigation the social phenomena can result many interpretations. Furthermore, in critical theory, practical issues can construct the knowledge. It tends to change the certain conditions through criticizing the practical, politics, and social issues. Therefore, the results can be subjective.
Furthermore, ontological assumption concerns on the nature of the world and human being in social contexts (Alan Bryman, 2001). There are different assumptions to see the world as outside individual. Therefore, ontology in normative emphasis that social phenomenon is independent from other factors. The world is one that there are no other perceptions. In contrast, interpretive emphasize that the world in social phenomena has different meanings. One factor influences the change in social context. As a result, different researches can have different conclusions for one observation. On the other hand, critical theory paradigm tends to see the world as something that has to change. It involves criticizing and the social phenomena and changing it based on the interrogations of the phenomena both social and individual.
Finally, methodological assumption focuses on analysis of the methods used for gaining the data (Louis Kohen, Lawrence Manion, Keith Morrison, 2001). In normative paradigms, scientific method, quantitative is used to observe the objects. It uses mathematics calculation to generalize the finding and test the theory. In contrast, an interpretive paradigm uses observation, fieldwork note to investigate the object. In short, an interpretive paradigm tends to use qualitative methods for observation. As a result, the findings can be open to many interpretations. On the other hand, methodology in critical theory tends to use both quantitative and qualitative approaches. Quantitative to control the social setting when doing the actions and qualitative to observe the changes that happened after the actions are given.