Experimental Group: Definition & Explanation

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  • 0:00 Experimental Group
  • 1:30 Setting Up the…
  • 2:02 Use Only One Variable
  • 2:42 Identifying the…
  • 3:42 Lesson Summary
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Lesson Transcript
Instructor: Lisa Roundy

Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.

An experimental group is used in an experiment to test a variable. It is the group to which the test variable is administered. Learn more about how an experimental group works in this lesson, and test your knowledge with a quiz at the end.

Definition of an Experimental Group

You usually store your microwave popcorn in the kitchen cabinet, but you read an article that recommends storing it the refrigerator. You want to find out if microwave popcorn actually pops better if it is stored in the refrigerator. You have two bags of popcorn, so you keep one in the cabinet and place the other in the refrigerator. The next day, you pop each bag of popcorn for the same amount of time in the microwave. You measure the amount of popcorn that popped in each bag to see which bag produced more.

You just created an experiment to test whether storing the popcorn in the refrigerator makes it pop better. There must be at least two groups in any valid experiment: the experimental and the control group. In this example, your experimental group is the bag of popcorn you placed in the refrigerator. An experimental group is the group that receives the variable being tested in an experiment. The control group is the group in an experiment that does not receive the variable you are testing. For your experiment, the bag of popcorn that remained stored in the cabinet is the control group. The only difference in the two groups is where the popcorn is stored. This means that storing the popcorn in the refrigerator is the variable, the condition that is allowed to change.

Setting Up the Experimental Group

There are two important things you need to know when you are setting up an experimental group. First, you must know exactly what variable you're going to be testing. Then, you must know how you are going to measure the results from the experimental group. In order to measure the results, you must have some way of making a comparison. Comparing the results from the experimental group with the results of the control group is one way to measure the results you obtain from the experimental group.

Think about how the results of the popcorn experiment were measured. You measured the amount of popcorn that popped in each bag to see which bag produced more. Let's say that the control group produced four cups of popcorn and the experimental group produced five cups of popcorn. What conclusion could you make from this information?

Use Only One Variable

In order for you to know exactly what causes a difference in the results between groups, only one variable can be measured at a time. For this reason, it's important that you only test one variable in the experimental group. If you tried to test more than one variable, you would not be able to tell which one was responsible for any differences that occurred.

For example, if you popped each bag of popcorn in the previous experiment at different power settings on the microwave, you would have two variables in the experimental group. You wouldn't know if the different results in the two groups was due to storing the popcorn at different temperatures or using different power settings on the microwave.

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