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Intro to Power
Paired Samples T-test Independent Samples T-test Multiple Regression One Way Analysis of Variance



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.


· Introduction 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 original spot.

· 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!

· Evaluation.

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!

· Lessons.

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:

  1. Read the Welcome information
  2. Go through the Introduction to Power Analysis power-point presentation.
  3. Read the Introduction to nQuery page.
  4. Open up the nQuery software (best if it is running as you go through the examples) and choose your lesson!
  5. Enjoy and learn! Remember to fill out the evaluation when you are finished.

Thank you for visiting our site! Please send questions and comments to ann.oconnell@uconn.edu


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