Answer:
Interrupted time-series design
Step-by-step explanation:
In scientific studies, this design is known as an Interrupted time-series design. Basically, it is when a researcher analyses a long-term period before and after an interruption for whatever reason in order to determine the extent to which the interruption/intervention affected the results of the study. In this experiment, Dr.Fletcher is examining the results between a span of 6 weeks from the point of joining the fraternity/sorority.