Question

In a new trial to test the effectiveness for a new type of medicine, why is it necessary for one group to receive a placebo?

Answer 1

Answer:

To serve as control experiment.

Explanation:

Hope it helps.

Answer 2

It is necessary in order to have a control group.
Explanation:
By having a placebo group one can observe whether or not the one with the new type of medicine have any consistent and real changes after taking the medicine.