Holders of a doctorate are expected to contribute to their discipline or profession through independent scholarship.
The dissertation provides students with first-hand experience in making such a contribution, requiring them to identify and define a research problem or area of investigation; devising or selecting a methodology for systematically looking into the problem; and summarizing the results of that inquiry, noting how the findings make an original contribution to theory or educational practice.
The dissertation is the culmination of a doctoral degree. It contributes new knowledge or a reinterpretation of existing knowledge to the area investigated.
A dissertation can be theoretical in nature, employing rigorous research techniques to the investigation of questions focusing on pedagogy, the knowledge area, or a combination of both.
Alternatively, a dissertation can be practice-oriented, focusing on new and replicable ways of teaching within the knowledge area. If you choose to concentrate on a knowledge area, then one chapter or an appendix of the dissertation must discuss suitable instructional procedures related with the topic.