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How Many Subjects?

How Many Subjects?
Statistical Power Analysis in Research

Second Edition

February 2015 | 160 pages | SAGE Publications, Inc

With increased emphasis on helping readers understand the context in which power calculations are done, this Second Edition introduces a simple technique of statistical power analysis that allows researchers to compute approximate sample sizes and power for a wide range of research designs. Because the same technique is used with only slight modifications for different statistical tests, researchers can then easily compare the sample sizes required by different designs and tests to make cost-effective decisions in planning a study. These comparisons demonstrate important principles of design, measurement, and analysis that are rarely discussed in courses or textbooks, making this book a valuable instructional resource as well as a must-have guide for frequent reference. 

1. The Rules of the Game
Exploratory Studies

Hypothesis Formulation

Null Hypothesis


The Statistical Test

Effect Sizes: Critical, True, and Estimated


2. General Concepts
Introduction to the Power Table

Statistical Considerations

3. The Pivotal Case: Interclass Correlation
The Intraclass Correlation Test

The ANOVA Approach to Intraclass Correlation Test

Normal Approximation to the Intraclass Theory

Non-Central t

Variance Ratios


4. Equality of Means: Z- and T-Test, Balanced ANOVA
Single-Sample Test, Variance Known: z-test

Single-Sample t-test

Two Sample t-test

An Exercise in Planning

Balanced Analysis of Variance (ANOVA)

5. Correlation Coefficients
Intraclass Correlation Coefficient

Product-Moment Correlation Coefficient

Rank Correlation Coefficients

You Study What You Measure!

6. Linear Regression Analysis
Simple Linear Regression

Experimental Design: Choosing the X-Values

Simple Linear Moderation Example

Problems: Collinearity and Interactions

Multiple Linear Regression

7. Homogeneity of Variance Tests
Two Independent Samples

Matched Samples

8. Binomial Tests
Single-Sample Binomial Tests

Two-Sample Binomial Tests

9. Contingency Table Analysis

The I X J x^2-test

An Example of a 3 X 2 Contingency Table Analysis

10. Wrap-Up

"Kraemer and Blasey provide an authoritative and readable introduction into applied statistical power analysis and its application with many common statistical procedures."

Glenn Gamst
University of La Verne

“This is a necessary text for anyone conducting research in the real world. Nowhere else will you find a better answer to the question, 'How Many Subjects?'” 

Bryan Rooney
Concordia University College of Alberta

Too advanced for the course; but on additional/further readings list.

Ms Susanne Kirchmair
Accounting , MCI Management Center Innsbruck
February 26, 2016

Helena Chmura Kraemer

Helena Chmura Kraemer is professor emerita of biostatistics in the Department of Psychiatry and Behavioral Sciences at Stanford University. She earned her BA in mathematics from Smith College, attended Manchester University on a Fulbright Scholarship, and received her PhD in statistics from Stanford University. Kraemer’s specific research interests include improvement to randomized clinical trial methodology, assessment of reliability and validity of diagnoses and clinical measurement, and developing mathematical models for specific problems in behavioral and clinical research. She has published extensively in the behavioral as well as... More About Author

Christine Margaret Blasey

Christine Blasey is a professor in the PGSP-Stanford Consortium, an academic program taught by faculty drawn from Palo Alto University and the Stanford University School of Medicine Department of Psychiatry. More About Author

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ISBN: 9781483319544

SAGE Research Methods is a research methods tool created to help researchers, faculty and students with their research projects. SAGE Research Methods links over 175,000 pages of SAGE’s renowned book, journal and reference content with truly advanced search and discovery tools. Researchers can explore methods concepts to help them design research projects, understand particular methods or identify a new method, conduct their research, and write up their findings. Since SAGE Research Methods focuses on methodology rather than disciplines, it can be used across the social sciences, health sciences, and more.