In experimental research, what is the independent variable?

In experimental research, the independent variable is the factor controlled by the researcher. This is the variable that the researcher manipulates in order to observe its effect on another variable, known as the dependent variable. By systematically changing the independent variable, researchers can determine whether and how it affects the outcomes of the study.

For example, if a psychologist is studying the impact of sleep on cognitive performance, the amount of sleep (the independent variable) would be manipulated by having different groups of participants sleep for various durations. The cognitive performance of the participants, measured through tests, would then be the dependent variable, which is expected to change in response to the manipulation of the independent variable.

In contrast, the other options refer to different aspects of variables in an experimental setup. The variable that is measured corresponds to the dependent variable, which is the response or outcome affected by the independent variable. The outcome variable also refers to the dependent variable, reinforcing the same concept. Lastly, the variable that remains constant is often referred to as a controlled variable, which is kept the same across all experimental groups to ensure that any observed effects can be attributed solely to the manipulation of the independent variable.