1.29 Dependent Variable

Dependent variables are one of three types of variables used in scientific experiments. Learn about the difference between dependent, independent, and control variables, and see how variables interact in an example of an experiment.

What Is a Dependent Variable?

Did you ever wonder why your mom always tells you to eat your vegetables? Is it just a mean trick that parents play so they can laugh as kids eat things they don’t like? Actually, your parents know that you are growing at a very fast rate and your body depends on the vitamins and minerals in vegetables.

This is the same idea behind a dependent variable, which is an element in an experiment that depends on something else. See, in any given experiment, there are three parts:

1. A control variable is the thing in an experiment that is unchanged and constant.
2. The independent variable is the variable that is changed on purpose to test the dependent variable.
3. The dependent variable, to explain again, is the variable that is affected by the changes made to the independent variable.

Just like your body depends on the vitamins in your vegetables, the dependent variable in an experiment depends on the independent variable. If you have a hard time telling the difference between the independent and dependent variables, try writing them in a cause-and-effect sentence. For example, ”Your body’s growth (dependent variable) depends on the amount of vitamins and minerals you consume (independent variable).” The sentence won’t make sense if you mix up the two variables!

1. Main points:

The text explains why parents encourage kids to eat vegetables: for the vitamins and minerals. It then relates this to the concept of a dependent variable in experiments.

2. Questions:

• Content Analysis: Why do your parents tell you to eat vegetables?
• Linguistic Analysis: What are the three main parts in an experiment?
• Socio-cultural Analysis: What do parents usually want for their children’s growth?

3. Further Discussion:

• Can you think of another example of a dependent and independent variable in everyday life?

4. Answers:

• Content Analysis: “Your parents know that you are growing at a very fast rate and your body depends on the vitamins and minerals in vegetables.”
• Linguistic Analysis: The three main parts in an experiment are a “control variable, independent variable, and dependent variable.”
• Socio-cultural Analysis: Parents usually want their children to grow “at a very fast rate and your body depends on the vitamins and minerals in vegetables.”

So, what’s something else you eat that helps you grow strong and healthy? 🥦🥕

Example Experiment

Jake wants to determine if the amount of sunlight a plant receives makes a difference in how much it grows. He takes three plants of the same type, puts them in the same type of soil, and gives them the same amount of water. He places one of the plants in the window for eight hours, another plant in the window for four hours, and one in a dark closet. At the end of one month, he measures all three plants and records his data.

In this scenario, there are multiple control variables. The plants, soil, and amount of water are all unchanged and constant throughout the course of the experiment. This ensures that the changes seen in the plants are not caused by the plant type, soil quality, and amount of water. The amount of sunlight is the independent variable. The amount of sunlight is the variable that you are changing to test the plant growth. The plant growth is the dependent variable. It’s what is being tested, and the plant growth depends on the amount of sunlight.

1. Main Points:

Jake conducts an experiment to determine if the amount of sunlight affects plant growth, keeping all other variables constant, and measures the growth after one month.

2. Questions:

• Content Analysis: What is Jake trying to find out through this experiment?
• Contextual Analysis: For how long does Jake conduct the experiment and how does he measure the outcome?

3. Further Discussion:

Is it important to keep all other factors like soil and water constant in the experiment? Why or why not?

4. Answers:

• Content Analysis: Jake is trying to “determine if the amount of sunlight a plant receives makes a difference in how much it grows.”
• Contextual Analysis: Jake conducts the experiment “at the end of one month,” and he “measures all three plants and records his data.”

Does this breakdown help you understand Jake’s experiment better? What do you think about the importance of keeping other factors constant in an experiment?

Lesson Summary

Okay, so let’s take a second to review what we’ve learned. Experiments have three types of variables: control, independent, and dependent variables. The dependent variable is what’s being tested in the experiment, and it depends on the independent variable. The independent variable is the variable that is changed on purpose to test the dependent variable, while the control variable is the thing in an experiment that is unchanged and constant. Writing the variables in a cause-and-effect sentence may help you determine which variable is the dependent variable.