In a controlled expierment, what is the expieremntal group compared to?

In a controlled experiment, the control group is compared with an experimental group.  

Explanation:

A set of variables or data is considered as the control group that remains fixed or constant in its normal usual state; while all the other variables or data are identical with this control group, except one independent variable at a time. This is to observe the changes when that one variable is allowed for variations at a time.

This independent variable which undergoes changes is in the experiment group while the remaining constant group is the control group. The dependent variable changes with changes in the independent variable.

By comparing the control group against the experimental group, uncertainty in results are avoided.

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velocity and height