What is control group?

Answer 1

When you are doing a test of a drug, the control group is the group that gets the placebo.

If you want to see if a drug will work the way that you want, you need to give it to two groups. One group that will get the drug and one that will not. But, they will get something that looks just like the same. The same color, size, etc.

The one that gets the placebo (fake) is called the control group.