Research, however, must be and we must not only be able to trust that we are measuring what we intend to measure, but that we can reliably obtain the same type of results each time we give the study.

The words needed to complete the sentence structure are quantitative and qualitative. They are the types of research that further investigates the study. In a qualitative research, it is the deeper investigation of the paper which uses some methods like focus groups. Meanwhile, a quantitative research gathers data through surveys and audits.