What is a Delimitation?

A delimitation is a choice that you made to set the parameters of the study. This is why scope and delimitations are often presented together. Again, we turn to Creswell for a terrific, easy-to-understand explanation:

Delimitations are choices made by the researcher which should be mentioned. Delimitations define the parameters of the investigation. In educational research the delimitations will frequently deal with such items as population/sample, treatment(s), setting, and instrumentation. (Creswell,
2004)

Just in case you missed it, delimitations are not to be confused with limitations.