Independent and Dependent Variables


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In an experiment, the independent variable is the variable that is changed by the experimenter, and the dependent variable is the variable that is measured to see how it changes in response to the independent variable.

The independent variable is the factor that the researcher intentionally manipulates or controls in an experiment. It is the cause or input that is expected to have an effect on the dependent variable. Here are a couple of examples:

  • A study investigates the effect of different study durations on exam scores. The independent variable in this case is the "study duration" because the researchers can control and assign participants to different study duration groups (e.g., 1 hour, 3 hours, 5 hours).
  • An experiment examines how different doses of a drug affect blood pressure. The independent variable is the "dose of the drug" because the researchers can administer varying doses to different groups of participants.

The dependent variable is the outcome or response that is being measured or observed in an experiment. Researchers are interested in understanding how variations in the independent variable lead to changes in the dependent variable. Unlike the independent variable, the dependent variable is not controlled by the researcher. Let's look again at our example experiments, this time identifying the dependent variables:

  • In the study investigating the effect of study duration on exam scores, the dependent variable is the "exam scores" because it is the outcome that is being measured based on the different study durations.
  • In the drug dosage experiment, the dependent variable is "blood pressure" since it is the response that is being observed in participants after administering varying doses of the drug.