Experimental Method: An In-Depth Look

Educ 241 (Research Methods in
Education)

 An attempt by the researcher to maintain
control over all factors that may affect the
result of an experiment. In doing this, the
researcher attempts to determine or
predict what may occur (Key, 1997).
 The major feature that distinguishes
experimental research from other types
of research is that the researcher
manipulates the independent variable
(Siegle, 2017).

 It is a blueprint of the procedure that
enables the researcher to test his
hypothesis by reaching valid
conclusions about relationships between
independent and dependent variables. It
refers to the conceptual framework
within which the experiment is
conducted.

 It guides the experimental study by
specifying:
1. what independent variables are to be
manipulated;
2. what dependent variable are to be
measured;
3. what levels of experimental treatment
are to be used;
4. how to select test units and assign
them to different groups;

 It guides the experimental study by
specifying:
5. how to control for selection bias
and
6. how to minimize the influence of
extraneous variables on the
result of the experiment.
 the basic idea of experimental design involves
formulating a question and hypothesis, testing
the question, and analyzing data (Biddix, 2017).

 It is also referred to as the experimental
variable, the cause, or the treatment, is
that activity or characteristics believed
to make a difference. It has levels,
conditions, or treatments.
Note:
Experimenters may manipulate
conditions, or measure and assign
subjects to conditions; supposed to be
the cause.

Examples:
 teaching method;
 type of teaching material;
 a reward;
 a period of exposure to a particular
condition;
 an attribute such as sex or level of
intelligence.
 may be classified as treatment variables and
attribute variables.

Treatment variables are those that the
experimenter manipulates and to which
subjects are assigned.
Attribute variables are those characteristics
that cannot be altered by the experimenter,
such as age, sex, race and intelligence level. The
experimenter can decide to include or remove
them as variables in the study.

 It is also referred to as the criterion variable,
effect or posttest, is the outcome of the study,
the change or difference in groups that occurs
as a result of manipulation of the independent
variable measured by the experimenter.
Examples:
 test score
 mental ability of the participants
 the number of errors
 the mental health

 These are the held constant by the
experimenter to eliminate them as
potential causes.
Example:
Only research participants who
have been problems with anxiety or
depression (Psychiatry)

 These are allowed to vary freely to
eliminate them as potential causes.
Many other characteristics of the
research participants, as long as they
really do vary freely, might include age,
personality type or career goals.

 These vary systematically with the
independent variable; may also be a
cause. Good experimental designs
eliminate them.
 Raagas (2006) considered these as
extraneous variables.

 Creating different level of the
independent variable.
 The independent variable is manipulated
and the effect of each level of
manipulation on the independent variable
is observed (Raagas, 2006)
 Manipulation in instruction and size of
groups but it can not manipulate the
gender and the socioeconomic status.

 It refers to efforts on the part of the
researcher to remove the influence of any
variable (other than the independent
variable) that might affect performance on
the dependent variable (Gay, 1996)
 There are really two different kinds of
variables that need to be controlled:
subject variables, and
environmental variables

 subject variables
such as reading readiness, variable on
which subjects in the different groups
might differ.
environmental variables
 such as learning materials, variable which
might cause unwanted differences
between groups.

 Methods of experimental control include:
(a)physical control;
(b)selective control; and
(c)statistical control

(a) physical control
- which controls non experimental variables
that affect the dependent variable.
(b) selective control
- which manipulates indirectly by selecting in and
out variables that cannot be controlled.
(c) statistical control
- where variables conducive to physical or
selective manipulation may be controlled by
statistical technique, e.g. covariance.

Experimental studies undergo similar steps as
other research studies, which includes:
1. selection and definition of a problem;
2. selection of subjects and measuring
instruments;
3. selection of designs;
4. execution of procedures;
5. analysis of data; and.
6. formulation of conclusions

Key (1997) mentioned the following steps
when conducting experimental studies:
1. identify and define the problem;
2. formulate hypotheses and deduce their
consequences;
3. construct an experimental design that
represents all elements, conditions and
relations of the consequences;

Key (1997) mentioned the following steps
when conducting experimental studies:
4. conduct experiment;
5. compile raw data reduce to usable
form ; and.
6. apply the appropriate test of
significance.

THREATS TO EXPERIMENTAL
VALIDITY
INTERNAL
VALIDITY
• Refers to the
condition that
observed
differences on
the dependent
variable are a
direct result of
manipulation of
the independent
variable.
EXTERNAL
VALIDITY
• Refers to the
condition that
results are
applicable to
groups and
environments
outside of the
experimental
setting.
ECOLOGICAL
VALIDITY
• Refer to the
degree to which
results can be
generalized to
other
environments.

 Are often considered as the most
“rigorous” of all designs.
 Probably the “strongest” design with
respect to internal validity.

A. Group Experimental
Designs1. Pre-Experimental Designs
- The One-Shot Case Study
- The One-Group Pretest-Posttest Design
- The Static-Group Comparison
2. True Experimental Designs
- The Prettest-Posttest Control Group
Design
- The Posttest-Only Control Group Design
- The Solomon Four-Group Design

A. Quasi-Experimental
Designs
1. The Nonequivalent Control Group Design
2. The Time-Series Design
3. Counterbalanced Designs
4. Factorial Design

REFERENCES
Prado, N. I., et.al. 2011. Research Methods. Philippines: Central Mindanao
University-IMDC. 12:205-209.
Authors Cited by Prado, N. I, et all
Davis, J. 2007. Experimental Research Methods. Metropolitan State College of Denver.
Gay, L.R. 1992. (4th Ed.) Educational Research-Competencies for Analysis and Application.
Maxwell Macmillan, Canada Inc.
Key, J.P. 1997. Research Design in Occupational Education. Oklahoma
State University. Retrieved from
http://www.okstate.edu/ag/aged.html.
Raagas, E. L. 2006. Experimental Designs. Lecture Notes shared during the PAGE Zonal
Area Conference, VIP Hotel Cagayan de Oro City.
Trochim, W. 2006. Research Methods Knowledge Base. Retrieved from
http://socialresearchmethods.net/ kb/ deserper.htm.

Educ 241 (Research Methods in
Education)
JAMES L. PAGLINAWAN, PhD
Professor
MARY MENDJILL CECILIA J. ROMERO
MS GEN SCIENCE EDUCATION

Experimental Method: An In-Depth Look

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