The term controlled experiment means you have all the control over what is being exposed to your variable. The control of an experiment means that you don't change any variables so you can compare them to the rest of the trials.
Work Step by Step
In a controlled experiment only one variable is tested an changed; the rest of the variables are kept the same. In a controlled experiment, there is also a control group. The control group has no variables that are changed and it is used as a comparison for the experimental group. This allows the researcher to easily determine how changes in the variable affect the outcome of the experiment.