An isolate population.
The study tried to isolate the effects of changing schools on student performance.
An example of isolate is when you turn everyone against your enemy, causing him to be alone.
An example of isolate is when you separate one part of a problem from the others so you can focus on solving just that aspect of the problem.
An example of isolate is when you try to identify one secret ingredient in a recipe you are eating.
The police isolated the area until more help could arrive.
An immigrant who was isolated by his poor language skills.
A system of government that isolated its citizens from foreign ideas.