Case studies do not compare individuals or groups to others randomly assigned to different treatments.

But this method can not truly identify effective schools because it compares different groups of students.

As stated earlier, height is a good way to compare living standards between geographical regions and ethnic groups of countries.

These scores were also used to validate the training by comparing experimental and control groups.

When comparing groups, you have to consider a lot more things than race.

The authors compared environmentalists to religious cults and superstitious groups of the past.

In 1999, researchers compared younger and older groups of Bangladeshis.

But they did not compare groups of loans by race to see if there were broad patterns of discrimination.

The case against salt has been made chiefly by comparing groups across cultural boundaries.

For comparing randomized groups, the question is "What is the effect of the particular screening program in the intervention group?"