An experiment is designed so that you can observe the differences between the experimental group and the

Control group

Explanation:

A controlled experiment is one in which a control group is used to compare with an experimental group in a test of a causal hypothesis. The control group is the group that, on an experimental level, is subject to pretest and posttest, but not to treatment or intervention. Thus, the control group differs from the experimental group only in the absence of intervention or impact of the experimental (independent) variable, or its manipulation being equivalent from the point of view of sampling to the experimental group.

not sure if this what   you'r looking for would be percent composition