"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.
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.
Type of Material:
The site is a tutorial that contains self-test items.
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.
Evaluation and Observation
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.
The hypothetical "background" experiment elicited concerns about the ethics of the study and some of the possible threats were not very meaningful, likely, or believable.
Potential Effectiveness as a Teaching Tool
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.
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
Navigating the site is very easy. The links to other topic areas or related sources are conveniently located for timely referral.