There are four ontologies / epistemologies by which research in the academy is undertaken and also put into practice in the real world. There is a lot of rhetoric about them but I tend to see methodology and practice through the lens of a person whose most loved one (a parent, sibling, cousin, spouse, sweetheart, friend or business partner) is suddenly rushed to hospital in a critical medical emergency condition and has to make important decisions based on the findings or assessments of a surgeon or physician.
The Empiricist, will tell you based on scans and blood tests and observations or she knows empirically (with 98% accuracy) your loved one has illness A with M prognosis.
The Positivist, will tell you based on observations of symptoms (with considerable certainty) your loved one has has condition B with prognosis N.
The Realist, will tell you based on tests and observations of symptoms (again with considerable certainty) your loved one has condition C with prognosis O but there maybe underlying causes or problems yet to be discovered.
The Post-Modernist, will tell that the disease your loved one has is ‘socially constructed’ and (with considerable certainty) no one knows anything about the condition D which is a discourse and therefore no prognosis is possible.
Which of these doctors will you take most and least seriously? That is research and practice methodology for you.