Scientists have developed a new type of margarine containing plant ingredients they think will lower blood cholesterol levels in
people who use the margarine. They want to test this by having some people use the new margarine for a while and then compare their cholesterol levels with those of a group of people who use regular margarine. This is an example of what type of research design?
An intervention study is a type of controlled clinical trial in which an intervention is applied to a group of people and the outcome is compared to a similar group without the intervention. An example of this type of study is shown in the question above, where a margarine which vegetable ingredients (which is the intervention) will be given to a group of people, so that their blood cholesterol levels are compared to the cholesterol levels of a group of people who didn't use this margarine.
