The part that is held for comparison is called "the control".
It can also be called the "independent variable" depending on what your teacher uses.
the CONTROL for the experiment
the control
Control(:
The Control Group
Controlled Variable
The control of an experiment is the part of an experiment that does not change, and is strictly used as a comparison to the variable that is being tested.
Controls or Control group
control group
the control group
The control group
The most crucial part of an experiment always is the control or pattern.
control group