Research can be classified as

Classification by purpose yields basic, applied, and action research as one legitimate scheme.

Classification by data type yields quantitative and qualitative research as another legitimate scheme.

Classification by method yields philosophical, historical, survey, and experimental research as a further scheme.

All three schemes are valid simultaneously, and only an all-inclusive category captures them together.

These typologies overlap, since a single study can be described along several dimensions at once.

Purpose, approach, and method are the standard textbook bases for classifying research.