Instructors' Notes for the Power Tutorial
How the Power Tutorial fits into the typical statistics
course: The Power Tutorial is the fourth module of the WISE
tutorials. The Power Tutorial was designed with the assumption that
students are familiar with concepts covered in the first three WISE
tutorials: 1) Sampling Distribution,
2) Central Limit Theorem, and 3)
Hypothesis Testing. The Power Tutorial is a
self-contained lesson that does not depend on any of the other modules,
although some specific prerequisite knowledge is required.
When to use the Power Tutorial? Instructors often introduce
statistical power along with or immediately following hypothesis
Teaching Theory vs. Computations: The goal of the WISE
Power Tutorial is to introduce the student to the four interconnected
concepts that are involved in power analyses (Power, Effect size, Alpha,
and Sample size). A one-tailed Z test is well suited for this purpose,
and the WISE Power Applet is designed to show these interconnections.
These same four interconnected concepts are keys to understanding power
analysis as it is extended to more complex designs.
In the main tutorial, we do not focus on hand
computations because there are wonderful computer programs that can do
the calculations much more quickly and accurately. Nonetheless, it may
be useful for students to work through some simple examples that
demonstrate the concepts. The short tutorial on Power Calculations
may be useful for this purpose.
Suggestions for Using the Power Tutorial
- Pre-lecture assignment
- Live In-class demonstration
- Laboratory assignment
- Post-lecture assignment
How you choose to incorporate this tutorial may depend on students’ level of computer literacy,
computer resources available at your school, and class time restrictions.
Here are a few suggestions:
1. Pre-lecture Assignment
Assign the module as an independent exercise for students to
introduce the concept of statistical power.
This will allow you to use more class time for in-depth discussions and activities
instead of a full lecture.
2. Live In-class Demonstration
As part of either a lecture or guided lab assignment, the Power applet itself
may be used by the instructor to demonstrate relationships among the
components involved in statistical power. Some instructors may choose to
step through parts or all of the tutorial in a demonstration mode. This demonstration
may serve as a stimulus for classroom discussion and/or introduction to an assignment
for students. See our
step-by-step guide for an
example of a live demonstration using the applet.
Demonstration Guide |
Instructions for Using Applet
3. Laboratory Assignment
The WISE modules can be used as laboratory assignments. They are
designed to be completed within about 45 minutes, though of course some
students may require more time. Students may be required to turn in lab
reports that include a record of the simulated sample findings and their
responses to short essay questions.
4. Post-lecture Assignment
After your presentation of the concepts of statistical power, the
module can be used to demonstrate lecture points and give students
practice using the concepts. This applet allows students to gain a
perspective on the concepts that complements a lecture or other
presentations. The more perspectives students are exposed to in the
course of instruction, the more likely they are to understand and retain
the material. Students may be asked to use the Power tutorial on their own and turn
in the lab sheets.
- Multiple-choice questions - The multiple-choice questions
provide feedback on both correct and incorrect responses. However, no record is kept of
student answers. Instructors could ask students to turn in their
- Essay questions - There are
after the main part of the module. These questions are designed to examine conceptual understanding of the topic.
You may want students to download
and complete this portion of the module and hand in their responses
for your evaluation. This will give you an opportunity to evaluate what your students have
learned. We have not posted answers to these questions.
Teaching Practical Power Analysis
An excellent free program
for power analysis is G*Power which is loaded with options for analyses with tests using
F, t, z, chi-square, and
exact distributions. For example, within F are tests for ANOVA, MANOVA,
Hotellings T, and Multiple Regression. G*Power can be downloaded from:
We hope this tutorial and associated applet are helpful for you and your students, and we
welcome your feedback on this tutorial and other aspects of the WISE site.
Please send your comments to firstname.lastname@example.org.
Questions, comments, difficulties? See our
technical support page or contact us: email@example.com.