Experimentation

Independent, Dependent, and Control
Variables
Type of psychology: Psychological methodologies
Fields of study: Experimental methodologies; methodological issues
The scientific method involves the testing of hypotheses through the objective collection
of data. The experiment is an important method of data collection in which the researcher
systematically controls multiple factors in order to determine the extent to
which changes in one variable cause changes in another variable. Only the experimental
method can reveal cause-effect relationships between the variables of interest.
Key concepts
• control group
• control variables
• dependent variable
• ecological validity
• experiment
• field experiment
• hypothesis
• independent variable
• random assignment
Psychology is typically defined as the science of behavior and cognition and
is considered a research-oriented discipline, not unlike biology, chemistry,
and physics. To appreciate the role of experimentation in psychology, it is
useful to view it in the context of the general scientific method employed by
psychologists in conducting their research. This scientific method may be
described as a four-step sequence starting with identifying a problem and
forming a hypothesis. The problem must be one suitable for scientific inquiry.
Questions concerning values, such as whether rural life is “better”
than city life, are more appropriate for philosophical debate than scientific
investigation. Questions better suited to the scientific method are those that
can be answered through the objective collection of facts—for example,
“Are children who are neglected by their parents more likely to do poorly in
school than children who are well treated?” The hypothesis is the tentative
guess, or the prediction regarding the question’s answer, and is based upon
other relevant research and existing theory. The second step, and the one
with which this article is primarily concerned, is the collection of data (facts)
in order to test the accuracy of the hypothesis. Any one of a number of methods
might be employed, including simple observation, survey, or experimentation.
The third step is to make sense of the facts that have been accumulated
by subjecting them to careful analysis; the fourth step is to share
any significant findings with the scientific community.