Answer: The group that is being tested.
Explanation:
When the chemical is introduced to the cloth is tested by two group of people. One group used the new chemical on the cloth and the other group does not used the chemical on the cloth.
The group that used the chemical on the cloth will be known as the experimental group because they are experimenting the chemical on the piece of cloth.
The other group is not using the chemical on the cloth is not performing any experiment.