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You need to set up a true experiment to test a hypothesis and demonstrate a cause and effect relationship. This lesson will teach you how this is accomplished and when you are forced to use other research designs.

Example and Definition

Let’s imagine that you recently went out dancing with your friends at two different clubs. The first dance club had a disco ball hanging from the ceiling, and the second club did not. You started wondering if dancing under a disco ball made people dance better. You want to prove that a true cause and effect relationship exists between the disco ball and better dance moves. How would you go about testing this idea?Since you want to demonstrate a cause and effect relationship between the disco ball and better dance moves, you would need to perform a true experiment.

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In a true experiment, effort is made to control all influences other than the ones that are being studied.

Experimental Research

True experiments are used in human growth and development research whenever they are feasible. This is because they are the only way to prove the existence of a cause and effect relationship between two variables. A true experiment will include all parts of the experimental process. To understand what this means, let’s walk through the process of developing your experiment to test whether a disco ball makes a person dance better.First, you will develop a hypothesis.

A hypothesis is a testable statement that is logically derived from theory or observation. Based on your observations at the dance clubs last weekend, your hypothesis is that a person will dance better when a disco ball is present.Now that we have your hypothesis, we need to talk about variables. A variable is an aspect of the research environment that can change. Controlling variables allows the researcher to determine a cause and effect relationship between what is being studied. In order to test for one variable, the researcher needs to have full control over all aspects of the environment. Then one aspect, or variable, is manipulated.

The variable that is manipulated in an experiment is called the independent variable. In your experiment, the independent variable is the disco ball. Another aspect, or variable, is measured. The researcher does not control this variable.

The variable that is measured in an experiment is called the dependent variable. In your experiment, the dependent variable is dance ability. So, you have your hypothesis and variables, but how do you test the independent variable? Let’s keep setting up the experiment and find out.If you want to test your hypothesis, it is obvious that you’re going to need some dancers. You would want to have a large number of test subjects with varied dancing skills to test. Once you have your test subjects, you need to split them into two separate groups. There must be at least two groups in any valid experiment: the experimental group and the control group.

An experimental group is the group that receives the variable being tested in an experiment. In your experiment, it is the group that will dance under the disco ball. The control group is the group in an experiment that does not receive the variable you are testing.

In your experiment, this would be the group that does not have a disco ball to dance under.Each group would be selected as a random sample. A random sample occurs when every individual in the group being studied has an equal chance of being selected. You now need to put judges in place to score the dancers in each of your two groups.

The judges will rate each dancer’s ability on a scale from 1-10. These scores will be used as results from each of the groups.How are you going to measure these results to test your hypothesis? 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 from the control group is one way of doing this.

On a scale of 1-10, dancers from the experimental group (with the disco ball) received an average score of nine. Dancers from the control group (without the disco ball) received an average score of four. This data supports your hypothesis that a disco ball makes people dance better! You have completed a true experiment and found a possible cause and effect relationship: The disco ball causes the dancers to perform better.

When a True Experiment Is Not Used

Now you know that a true experiment allows a researcher to have full control, yields the most valid information and demonstrates cause and effect relationships. So why are other types of research designs sometimes used? In human growth and development research, other methods of research are a common and often necessary replacement for a true experiment. This is usually because it is not possible to utilize a random sample.

This may be due to ethical concerns or lack of practicality.Imagine trying to create a random sample when you are researching the effects of child abuse. If a parent is randomly selected from a group of study participants for the experimental group, they will be forced to abuse their children throughout the study. This would be unethical and unacceptable!When a true experiment is not feasible, there are many different ways we can go about finding answers. We can examine existing information to look for data that can be manipulated to show possible relationships, we can observe what we see in the world around us or examine specific groups in other ways. The results from other research designs may not prove cause and effect, but the results can be used to infer this relationship.

Lesson Summary

In a true experiment, every effort is made to control all influences other than the ones that are being studied.

This type of research will provide the most reliable information but is sometimes unethical or impractical for human growth and development research. A true experiment will include all parts of the experimental process.First, you will develop a hypothesis. A hypothesis is a testable statement that is logically derived from a theory or observation.

Then you will identify the variables. A variable is an aspect of the research environment that can change. Controlling a variable is what allows a researcher to demonstrate a cause and effect relationship. There are independent variables and dependent variables in an experiment.Next, test subjects are chosen and split into two separate groups through random sampling. These two groups are the experimental group and the control group.

A random sample occurs when every individual in the group being studied has an equal chance of being selected. After measuring the results from each of your groups, you will compare the results from the experimental group with the results of the control group. This comparison is what will either support or reject your hypothesis.

Even though other research designs are often used and can provide useful results, the results they provide must be inferred to some degree. A true experiment is the only research method that can prove the existence of a cause and effect relationship between two variables.

Learning Outcomes

When this lesson is done, you should be able to:

  • Describe what a true experiment is and how it is set up
  • Define hypothesis and variables
  • Differentiate between independent and dependent variables, as well as between experimental groups and control groups
  • Understand what is meant by a random sample
  • List the benefits of true experiments
  • Explain when it would not be possible to set up a true experiment

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