Sponge's AP Psychology Vol. 3 - Overview of Experimental Research
- mbergman9
- Nov 9, 2015
- 3 min read
In an experiment, a researcher manipulates a variable to see if this manipulation will cause an effect. Manipulation sounds like something bad, but in this case think of manipulation like handling or changing something in the experimental group. The variable that is manipulated, or changed, is called the independent variable. By manipulating a variable in the experiment, researchers can see if this variable has an effect on another variable. The variable that we measure in an experiment to see if the independent variable has caused an effect is called the dependent variable. Experiment is the only type of research that demonstrates causation.
In basic experimental design, you will have a control group and an experimental group.
The control group is the status quo group. Nothing is done to this group. The independent variable is not introduced to this group at all. In order to know if the independent variable has an effect on the dependent variable, there has to be a baseline group with the "normal" conditions. This is the control group.
The experimental group is the group that receives the "treatment" which means that it is the group that receives the independent variable. By this group experiencing the independent variable, the researcher can see if the independent variable's introduction had an effect on the group. The researcher will know this by comparing the dependent variables between each group.
In the simplest design of experimental research, there is one control group and one experimental group, but there are other variations of experimental design. There should always be a control group, but there can be multiple experimental groups with various independent variables. Regardless, of how many experimental groups exist, one or many, there has to be many controls in place to keep the conditions the same between the groups.
How does someone get in the control or the experimental group?
Random assignment to the group is very important. One of the first lines of defense against flaws in experimental design is to make sure that individuals or organisms are assigned to groups using random assignment. Random assignment means that a method is used to ensure that each individual or animal has an equal chance of being assigned to either the control group or the experimental group. By using random assignment, the researcher is insuring that the deck won't be stacked. Random assignment shuffles the deck so we won't get all Aces in one group and all twos in another; instead we will have a mix of cards, or in our case subjects, in our groups.
In addition to random assignment, researchers must control for ANYTHING that might affect the dependent variable. The conditions between the groups must be the same. The only thing that should be different is the independent variable. Researchers must be on the lookout for factors that can affect the dependent variable such as time of day, temperature, lighting, noise, and so much more. Variables that go unnoticed, but are different between the groups are known as lurking variables. As you can imagine, experiments are very difficult to conduct and many studies in Psychology are not experimental.
Lastly, it is important for the participants in a study and the researchers to NOT know to which group they are randomly assigned. This is in order to avoid any bias that the researchers or participants may have for either the control or experimental group. This is known as a double-blind study.
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