Research Methods Module 4

1. EXPERIMENTS
MODULE 4

2. MODULE LEARNING OUTCOMES
After completion of Module 3, you should:
1. Understand the components of an experimental method plan
2. Understand the difference between a quasi-experiment and a true experiment
3. Be able to identify a control group experimental design and a pre-post experimental
design

3. EXPERIMENTS

4. An experiment is an empirical study in which certain conditions are produced deliberately and observed in
their effects. Participants are distributed randomly to experimental and control groups.
The purpose of an experiment is to explore a cause-and-effect relationship.
To qualify as an experiment, a study must have one or more treatments that are given by a researcher, or at
least given under the researcher’s directions, for the purposes of experimentation.
The treatments constitute the independent variable, the variable that is under the control of the
experimenter. The outcome variable is called the dependent variable. By definition, all experiments have at
least one independent variable and one dependent variable.

5. CONTROL GROUP DESIGN
A control group design is a design that
includes two groups, of which one (the
control group) will not receive the treatment
being studied in order to control whether the
effects that are observed in the treatment
group also occur without treatment or
whether they really can be located in the
treatment.
In a pre-post design, the initial situation is
measured in both groups (pre-test
measurement). Then the study group is
given the treatment (intervention).
Afterwards, both groups, the post-test
situation is documented.
PRE-POST DESIGN

6. TRUE EXPERIMENTAL AND QUASI-EXPERIMENTAL DESIGNS
True experimental designs have random assignments to comparison groups. Using random assignments to
groups controls all the threats to internal validity.
Unfortunately, it is often not possible to assign individual participants at random to treatment groups.
In a quasi-experimental design, there are two groups: an experimental group that receives the treatment
and a control group. Individuals are not assigned at random. Instead, the groups are preexisting groups.
This design is more useful when the pretest scores are similar and if you want to yield results for similar
demographic groups.

7. EXPERIMENTAL METHOD PLAN

8. COMPONENTS OF AN EXPERIMENTAL METHOD PLAN
In writing a survey methods section, follow this format:
1. Participants. The researcher should establish the selection, assignment, and number of participants who will
take part in the experiment.
2. Variables. The variables (independent and dependent) need to be specified so that it is clear to the readers
which groups are receiving the experimental treatment and which outcomes are being measured.
3. Instrumentation and Materials. The researcher should report on the way the observations are made at the
different stages of the procedures and report on materials used for the experimental treatment.
4. Experimental Procedures. The specific experimental design needs to be identified
5. Threats to Validity. Experimental researchers need to identify potential threats to the internal validity of their
experiments and design them so that these threats will not likely arise or are minimized.
6. The Procedure. The procedure for conducting the experiment needs to be described in details so that the
reader is able to understand the design being used, the observations, the treatment, and the timeline of the
activities.
7. Data Analysis. The researcher must tell the reader about they types of statistical analysis that will be used to
analyse the data from the experiment.
8. Interpreting Results. The final steps are to interpret the findings in light of the hypothesis or research
questions set forth in the beginning.
Creswell, Research Design: Qualitative, Quantitative, and Mixed Methods Approaches, 2014