Interpreting Independent and Dependent Variables for the GED Science Test

By Murray Shukyn, Achim K. Krull

Being able to interpret variables is an important skill that you will need for the GED Science test. Variables are anything that changes during the course of an experiment, and they come in the following two varieties:

  • Independent: An independent variable is the condition that the researcher chooses to change. If you’re testing how temperature affects pressure in a pressure cooker, the temperature of the water is the independent variable that you manipulate.

  • Dependent: A dependent variable is the result from manipulation of the independent variable. If you crank up the temperature of water in a pressure cooker, the dependent variable is the pressure, which rises accordingly.

For example, suppose a scientist designs an experiment to test how high different quantities of helium will lift his cat into the air. He buys balloons, string, helium, and a suitable harness for his cat. He ties the harness to his cat and starts filling the helium balloons and tying them to the harness. In this case, the independent variable is the amount of helium, and the dependent variable is the height his cat is lifted off the ground.

Here are some other examples of dependent and independent variables in scientific experiments.

  1. A scientist studies the impact of a medication on symptoms of the common cold. What is the dependent variable?

  2. To test her hypothesis that tasteless food will curb appetite, a scientist divides 40 chimpanzees into two groups and feeds one group a normal diet while feeding the other the same food with the taste removed. What is the dependent variable?

  3. An automobile manufacturer is designing a flex-fuel vehicle that can run on gasoline or E85 ethanol fuel and needs to know the difference in distance it can travel on a tank of gasoline or a tank of E85 ethanol. What is the dependent variable?

Check your answers:

  1. The cold symptoms — specifically whether the symptoms improve, worsen, or remain unchanged — are the dependent variable.

  2. Appetite, which would probably be measured by the quantity of food the two groups consumed, is the dependent variable.

  3. Distance is the dependent variable. The independent variable is the type of fuel.

The relationship between independent and dependent variables is often plotted on a graph, with each axis of the graph representing a different variable. On the test, you may be presented with a graph and asked to identify the dependent and independent variable.

An airplane manufacturer needs to test the effect of airspeed on lift. The test pilot increases the airspeed and records data from the instrument panel that indicates the change in altitude.

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The independent variable is ________, and the dependent variable is ________.

The independent variable is the condition that the test pilot is changing, which is the airspeed of the plane. The dependent variable is the lift, measured in altitude.