Scientific Variables

Independent Variable (Manipulated) The variable that is changed by the person doing the experiment. The person doing the experiment has control over this variable. This is the only variable that should be changed throughout the entire experiment. There should only be one independent variable in an experiment. When stating a hypothesis, the independent variable is the first variable. Many hypotheses use if…then statements. If this is the case then the independent variable is the “if” part.

Dependent Variable The dependent variable is what is measured either throughout the experiment or at the end of the experiment. The dependent variable changes because of the change that was made to the independent variable. There can be more than one dependent variable but most of the time only one variable is measured. When stating a hypothesis, the dependent variable is the second variable. The dependent variable is the “then” part of a hypothesis.

Control Group The control group is the group that you compare your experimental group to. This group receives no experimental treatment. The experimental group is changed but the control group is not. Control groups are used if there is expected to be a change such as an increase or decrease. The independent variable is not applied to the control group.

Constants Every variable in an experiment except for the independent and dependent variables are called constants. They are called constants because they should not change throughout the experiment. The reason why they should not change is because they can alter the results of your experiment. If any change occurs during the experiment we want it to be because of the change of the independent variable. In a good experiment, every variable except the IV and DV must remain the same.