What is a non-example of control variable?

A non-example of a control variable is a variable that is not intentionally kept constant or manipulated in an experiment. For example, in a study examining the effects of different teaching methods on student performance, the color of the walls in the classroom would be a non-example of a control variable because it is not being controlled or manipulated by the researcher. Non-examples of control variables can introduce confounding factors that may impact the results of an experiment.