What is a "control variable" in biology?

Answer by  Kristin (37)

A control variable is a condition that is held constant in an experiment. The control variables stay the same for all experimental conditions being tested. For example, to test the effect of medication you could administer three different doses, but the type of medication and route of administration would stay the same for all three dose trials.

Answer by  Suggestion (335)

The control variable is the item that you control in an experiment. In other words it is the item that has to remain constant during the experiment. It does not change.

Answer by  Anonymous

contro variable are quantities that a scientist wants to remain constant, and he must observe them as carefully as the dependent variables.