What is the variable that is actively changed or manipulated in an experiment?

In an experiment, the variable that is actively changed or manipulated is known as the independent variable. This is the factor that researchers alter in order to observe its effect on another variable, typically the dependent variable. By manipulating the independent variable, researchers can establish cause-and-effect relationships and determine how different levels or conditions of this variable influence outcomes.

For example, in a study examining the effect of different amounts of sunlight on plant growth, the amount of sunlight would be the independent variable, as the researcher can control how much sunlight each group of plants receives. The changes in plant growth observed as a result of altering the sunlight levels represent the dependent variable.

Other types of variables mentioned, like dependent variables, extraneous variables, and controlled variables, play different roles in an experiment. The dependent variable is what is measured or observed in response to the changes made to the independent variable. Extraneous variables are additional factors that may affect the outcome but are not the focus of the study, while controlled variables are kept constant to avoid influencing the results.