Method of Writing
Research Papers 2
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EXPERIMENTAL VS. NONEXPERIMENTAL STUDIES
Studies may have designs that are experimental, quasiexperimental, or nonexperimental. The fundamental
difference between experimental and nonexperimental study
designs rests in the use of a manipulation or treatment.
Experimental designs introduce a specific treatment and then
measure whether this treatment has an effect on some
outcome. In most social science disciplines, experimental
treatments tend to be “manipulations.” For instance, an
educational researcher may wish to find out whether students
remember basic grammar rules better if they receive online
grammar tutoring. The online tutoring is a “treatment” that
may or may not produce the desired effect.

Experimental and nonexperimental studies have
different designs, which are covered in more detail in
later topics. To determine if a design is experimental
or not, it helps to ask, “Will a treatment be introduced
in the study?” However, introducing a treatment is
not sufficient to make a study an experiment.
Experiments must meet a few other criteria. Because
experiments are trying to isolate the effect of the
treatment, it is important to be able to rule out other
factors. For this reason, a pretest measure is highly
desirable component of experimental designs.

One way to help reduce the plausibility of other
explanations is to have a control group that did
not receive the treatment, in addition to the
experimental group that received the
treatment. A true experiment will divide
participants into the control and experimental
groups randomly.

In many studies, it is possible to make the study blind,
which means that either the participant or the
researcher does not know who received a treatment
and who did not. In a study that is double-blind,
neither the participant nor the researcher knows who
is receiving the treatment. One instance might be an
education intervention in which those grading the
assignments do not know which students received the
experimental treatment and which were in the control
group.

Some studies may be quasi-experimental by meeting
some but not all of the criteria of an experiment.
When few of the basic experimental conditions can be
met, it is time to consider other possible quasiexperimental or nonexperimental designs because
each element that is missing or inadequate within an
experimental design weakens confidence in the
reported results. Sometimes, experimental conditions
are not possible, practical, or ethical, and
nonexperimental study is a better design.

In nonexperimental studies, researchers do not give
treatments. Rather, they observe participants in
order to describe them as they naturally exist,
without introducing manipulations or treatments.
Some common types of nonexperimental studies are
surveys, polls, interviews, and observation. These
methods may ask participants about their attitudes,
beliefs, and behaviors instead of observing them.
Generally, nonexperimental studies require a greater
accumulation of evidence to support claims.

Example
Fifty students are divided into two groups at random. One
group receives math instruction via a correspondence course
on the Internet. The other group is given instruction on the
same math skills using a traditional textbook. The purpose is
to see if instruction via the Internet is more effective than
traditional textbook instruction.
In the example, the group receiving the new type of
instruction via the Internet is the experimental group, while
the group receiving the instruction with a textbook is the
control group. This experiment is a true experiment because
all four conditions for an experiment are met: there is a
treatment, participants are measured before and after
instructions, there is a control and experimental group, and
participants are randomly assigned using appropriate random
assignment strategies.

By now, it should be clear that the purpose of
an experiment is to explore cause-and-effect
relationships (i.e., treatments are given to see
how they affect the participants). The next
topic describes how nonexperimental studies
are also sometimes used for this purpose.

TOPIC REVIEW
1. Are treatments given in nonexperimental studies?
2. In an experiment, Group A was given verbal praise
for being on time for appointments while Group B
was given no special treatment. Which group is the
control group?
3. Is it necessary to have at least two groups of
participants in order to conduct an experiment?
4. What is the purpose of a nonexperimental study?
5. Is a survey an experiment?
6. Does knowing that a multiple-choice test was used
in a study help a consumer of research determine
whether the study was experimental or
nonexperimental?

7. What is the purpose of an experiment?
8. A political scientist polled voters to determine their
opinions on a decision by the Supreme Court. Is this
an “experimental study” or a “nonexperimental
study”?
9. A teacher compared the effectiveness of three
methods of teaching handwriting by using different
methods with different students. Did the teacher
conduct
an
“experimental
study”
or
a
“nonexperimental study”?

DISCUSSION QUESTIONS
1. Suppose you read that an outbreak of intestinal disorders
occurred in a town and the source was traced to
contaminated chicken served in a popular restaurant. Is it
likely the study that identified the source was “experimental”
or “nonexperimental”? Why?
2. Have you ever conducted an informal experiment by giving
a treatment to a person or a group and then observing the
effects? If so, briefly describe it. Would you have
obtained better information by including a control group?
Explain.
3. Suppose you wanted to know whether having parents
read to preschool children has a positive effect on the
children's subsequent reading achievement. Do you think it
would be better to conduct an “experimental study” or a
“nonexperimental study”?

RESEARCH PLANNING
Considering your area of research interest, what type of
experimental study might reveal something of interest?
What nonexperimental approaches might be fruitful?

Good luck!