Final answer:
In a controlled experiment, the variable that the experimenter changes or manipulates is called the independent variable, and its influence on the dependent variable is measured while controlling other variables.
Step-by-step explanation:
In a controlled experiment, the variable that is purposely changed or manipulated is known as the independent variable. The independent variable is the factor that is being tested by the experimenter to observe its influence on the dependent variable, which is what is measured in response to changes in the independent variable. Any control variables, which may affect the outcome, are kept constant throughout the experiment to ensure that only the effects of the independent variable on the dependent variable are observed.