This website was designed to help address one of the most common questions
in research design: How many subjects do I need? As with many things
in life, this question is often easier asked than answered! Through
this website, and the associated tutorial using the nQuery power analysis
software, we have attempted to demystify much of the language, concepts
and formulas surrounding determination of an appropriate sample size
for a variety of research designs.
Our website contains several sections.
to power analysis.
o This brief power point presentation guides you through the very
basics of power analysis, highlighting factors related to statistical
power and determination of appropriate sample size.
· Introduction to nQuery.
o Although freeware for power analysis can be downloaded off the
web (see our links to other websites), we choose a popular and comprehensive
commercial software for use by the Power Project. The nQuery software
is flexible and easy to use, and emphasizes the notion of effect size,
rather than attainment of statistical significance, for the determination
of statistical power and appropriate sample size.
· Glossary of terms.
o Our website contains a glossary that explains most of the terms
common to studies of power analysis and sample size determination.
Clicking on any of the hotlinks can bring up the definition of that
term. Then, just hit the "back" button to return to your
· Links and Resources.
o Contains links to interesting and useful websites pertaining to
power analysis, statistics in general, and determination of appropriate
sample size. Also found here are references and other resources that
are often referred to in the field of research design. This section
is frequently being updated, so check back soon!
o This website is currently a work in progress. We hope to gain
a lot of good feedback from individuals "piloting" our website
and tutorial, so that we can improve the navigation and the information
contained on our site. The evaluation form can be answered online
and submitted directly to our data analyst!
o Finally, we've incorporated five "lessons," which we
use to anchor the concepts and procedures associated with power analysis
and sample size determination. These lessons are based on actual published
research studies selected from the social sciences. During the piloting,
you will be asked to review one of these lessons, which will take
you step by step through an application of the nQuery software.
o As of today, we have five lessons completed:
§ Paired-samples t-test
§ Independent samples t-test
§ Chi-square test
§ Multiple regression
§ One-way analysis of variance
Suggested path through the website:
- Read the Welcome information
- Go through the Introduction to Power Analysis
- Read the Introduction to nQuery page.
- Open up the nQuery software (best if it is running as you go through
the examples) and choose your lesson!
- Enjoy and learn! Remember to fill out the evaluation
when you are finished.
Thank you for visiting our site! Please send questions and comments
Ann Aileen O'Connell, Ed.D.
Associate Professor, Educational Psychology
Measurement, Evaluation and Assessment Program
Neag School of Education
University of Connecticut
Storrs, CT 06269-2064