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Peer Review

Experimental Design: Internal Validity

by Dr. Cheuk Ng , Dr. David Polson


Overall Numeric Rating:

4.5 stars
Content Quality: 4.2 stars
Effectiveness: 4.5 stars
Ease of Use: 5 stars
Reviewed: Feb 26, 2005 by Psychology
Overview: "Experimental Design: Internal Validity" is part of the courseware of the
Psychology Center of Athabasca University, an online and distance education
institution located in Alberta, Canada. It is a tutorial which is used in AU's
Experimental Psychology course and focuses on threats to internal validity in
experimental design. In Part 1, the author uses a
hypothetical experiment and discusses examples and nonexamples of each threat in
reference to this experiment. In Part 2, 36 hypothetical experiments must be
classified as internally valid or not.
Type of Material: The site is a tutorial that contains self-test items.
Recommended Uses: The material is intended as a resource for students studying internal validity
and threats thereto in experimental design. The site could be used to teach
students in research methods courses how to best design experiments and how to
assess the strengths and weaknesses of experiments.

Technical Requirements: None.
Identify Major Learning Goals: The tutorial is designed to introduce students to the concept of internal
validity in the design of psychological experiments, to identify and discuss
nine sources of threat to internal validity, and, through the use of numerous
hypothetical experiments, to have the student demonstrate his/her mastery of the
subject matter by indicating whether or not the hypothetical experiments are
internally valid.
Target Student Population: The tutorial is intended for college level students.
Prerequisite Knowledge or Skills: Completion of a basic psychology course and an introduction to statistics course
would be appropriate.

Evaluation and Observation

Content Quality

Rating: 4.2 stars
Strengths: The topic of internal validity and its threats is thoroughly examined, and the
hypothetical experiments and analyses used to assist students in identifying
threats to internal validity are very good.
Concerns: The hypothetical "background" experiment elicited concerns about the ethics of
the study and some of the possible threats were not very meaningful, likely, or

Potential Effectiveness as a Teaching Tool

Rating: 4.5 stars
Strengths: As teaching tool this online tutorial is excellent. The material is presented in
an orderly fashion, and the body of the presentation is consistent with that
which is outlined in the introduction. The tutorial has good examples,
nonexamples, and analyses of each of the nine threats to internal validity.
Concerns: The major strength of this site is also its potential weakness. Because the site
is so comprehensive and detailed, it requires one to spend a large amount of
time and effort to go through it. It might be better if the author chose the
most commonly occurring validity threats and highlighted these.

Ease of Use for Both Students and Faculty

Rating: 5 stars
Strengths: Navigating the site is very easy. The links to other topic areas or related
sources are conveniently located for timely referral.

Other Issues and Comments: