Answer:
intervention study
Step-by-step explanation:
The intervention study or research helps to examine the effects of an intervention of an outcome of interest. The main purpose of this type of study is to endenger the desirable of the individuals in need.
Such studies are often prospective.
In the context, scientist who have developed a new margarine containing plant ingredients. The scientists wanted to test the hypothesis whether consuming this new margarine lowers blood cholesterol in the body or not. They gave people to consume the margarine and is doing the research study. Such a research design is called as the intervention study.