What is a variable, and how are independent and dependent variables different?

What is a variable, and how are independent and dependent variables different?

• A. The independent variable is measured and observed.
• B. The dependent variable is the part that is kept the same.
• C. Independent and dependent variables are always identical.
• D. An independent variable is changed by the experimenter; a dependent variable is measured and observed.

Answer: (D)

In an experiment, you have something you change on purpose and something you observe or measure to see what happened. The thing you change is the independent variable. The thing you measure to see the effect is the dependent variable. For example, if you want to learn how different amounts of water affect plant growth, you would change how much water each plant gets (the independent variable) and you would measure how tall or how much the plant grows (the dependent variable). So the statement that fits best is: an independent variable is changed by the experimenter; a dependent variable is measured and observed. The other ideas mix up the roles—independent variable isn’t what you measure, keeping the dependent variable the same describes the controlled variables, and independent and dependent variables are not identical.

In an experiment, you have something you change on purpose and something you observe or measure to see what happened. The thing you change is the independent variable. The thing you measure to see the effect is the dependent variable.

For example, if you want to learn how different amounts of water affect plant growth, you would change how much water each plant gets (the independent variable) and you would measure how tall or how much the plant grows (the dependent variable).

So the statement that fits best is: an independent variable is changed by the experimenter; a dependent variable is measured and observed. The other ideas mix up the roles—independent variable isn’t what you measure, keeping the dependent variable the same describes the controlled variables, and independent and dependent variables are not identical.