Answer:
Experimental group.
Step-by-step explanation:
In a scientific experiment, there's often two groups: a control group and an experimental group. These two groups are the same, except that for the experimental group, an independent variable is changed. The idea behind this is that a change in the independent variable will yield a different result for the dependent variable. For this experiment, the independent variable is whether couples cohabitate before marriage or not, and the dependent variable is the divorce rate. The group of couples who do not cohabitate will be the experimental group, as the cohabitation variable is changed for this group.