THE ESSENCE OF MULTIVARIATE THINKING Basic Themes and Methods Multivariate Applications Series Sponsored by the Society of Multivariate Experimental Psychology, the goal of this series is to apply complex statistical methods to significant social or behavioral issues, in such a way so as to be accessible to a nontechnical-oriented readership (e.g., nonmethodological re- searchers, teachers, students, government personnel, practitioners, and other professionals). Applications from a variety of disciplines, such as psychology, public health, sociology, education, and business, are welcome. Books can be single- or multiple-authored, or edited volumes that: (1) demonstrate the application of a variety of multivariate methods to a single, major area of research; (2) describe a multivariate procedure or framework that could be applied to a number of research areas; or (3) present a variety of perspectives on a controversial topic of interest to applied multivariate researchers. There are currently nine books in the series: • What if there were no significance tests? co-edited by Lisa L. Harlow, Stanley A. Mulaik, and James H. Steiger (1997). • Structural Equation Modeling with LISREL, PRELIS, and SIMPLIS: Basic Concepts, Applications, and Programming written by Barbara M. Byrne (1998). • Multivariate Applications in Substance Use Research: New Methods for New Ques- tions, co-edited by: Jennifer S. Rose, Laurie Chassin, Clark C. Presson, and Steven J. Sherman (2000). • Item Response Theory for Psychologists, co-authored by Susan E. Embretson and Steven P. Reise (2000). • Structural Equation Modeling with AMOS: Basic Concepts, Applications, and Pro- gramming, written by Barbara M. Byrne (2001). • Conducting Meta-Analysis Using SAS, written by Winfred Arthur, Jr., Winston Ben- nett, Jr., and Allen I. Huffcutt (2001). • Modeling Intraindividual Variability with Repeated Measures Data: Methods and Applications, co-edited by D. S. Moskowitz and Scott L. Hershberger (2002). • Multilevel Modeling: Methodological Advances, Issues, and Applications, co-edited by Steven P. Reise and Naihua Duan (2003). • The Essence of Multivariate Thinking: Basic Themes and Methods by Lisa Harlow (2005). Anyone wishing to submit a book proposal should send the following: (1) author/title, (2) timeline including completion date, (3) brief overview of the book's focus, including table of contents, and ideally a sample chapter (or more), (4) a brief description of competing publications, and (5) targeted audiences. For more information please contact the series editor, Lisa Harlow, at: Department of Psychology, University of Rhode Island, 10 Chafee Road, Suite 8, Kingston, RI 02881-0808; Phone: (401) 874-4242; Fax: (401) 874-5562; or e-mail: [email protected]. Information may also be obtained from members of the advisory board: Leona Aiken (Arizona State University), Gwyneth Boodoo (Educational Testing Service), Barbara M. Byrne (University of Ottawa), Patrick Curran (University of North Carolina), Scott E. Maxwell (University of Notre Dame), David Rindskopf (City University of New York), Liora Schmelkin (Hofstra University) and Stephen West (Arizona State University). THE ESSENCE OF MULTIVARIATE THINKING Basic Themes and Methods Lisa L. Harlow University of Rhode Island LAWRENCE ERLBAUM ASSOCIATES, PUBLISHERS 2005 Mahwah, New Jersey London Senior Editor: Debra Riegert Editorial Assistant: Kerry Breen Cover Design: Kathryn Houghtaling Lacey and Lisa L. Harlow Textbook Production Manager: Paul Smolenski Full-Service Compositor: TechBooks Text and Cover Printer: Hamilton Printing Company This book was typeset in 10/12 pt. Times, Italic, Bold, and Bold Italic. The heads were typeset in Americana, Americana Italic, and Americana Bold. Copyright © 2005 by Lawrence Erlbaum Associates, Inc. All rights reserved. No part of this book may be reproduced in any form, by photostat, microform, retrieval system, or any other means, without prior written permission of the publisher. Lawrence Erlbaum Associates, Inc., Publishers 10 Industrial Avenue Mahwah, New Jersey 07430 www.erlbaum.com Library of Congress Cataloging-in-Publication Data Harlow, Lisa Lavoie, 1951- The essence of multivariate thinking : basic themes and methods / Lisa L. Harlow. p. cm.—(Multivariate applications book series) Includes bibliographical references and index. ISBN 0-8058-3729-9 (hardback : alk. paper)—ISBN 0-8058-3730-2 (pbk. : alk. paper) 1. Multivariate analysis. 2. Psychology—Mathematical models. I. Title. II. Series. QA278.H349 2005 519.5'35—dc22 2004028095 Books published by Lawrence Erlbaum Associates are printed on acid-free paper, and their bindings are chosen for strength and durability. Printed in the United States of America 10 9 8 7 6 5 4 3 21 Disclaimer: This eBook does not include the ancillary media that was packaged with the original printed version of the book. In memory of Jacob Cohen This page intentionally left blank Contents List of Figures and Tables xv Preface xxi I: OVERVIEW 1 Introduction 3 What is Multivariate Thinking? 3 Benefits 4 Drawbacks 6 Context for Multivariate Thinking 7 2 Multivariate Themes 10 Overriding Theme of Multiplicity 10 Theory 11 Hypotheses 11 Empirical Studies 12 Measurement 12 Multiple Time Points 13 Multiple Controls 13 Multiple Samples 14 Practical Implications 15 Multiple Statistical Methods 15 Summary of Multiplicity Theme 17 Central Themes 17 Variance 18 Covariance 18 Ratio of (Co-)Variances 18 Linear Combinations 19 Components 19 Factors 20 Summary of Central Themes 20 Interpretation Themes 21 Macro-Assessment 21 vii viii CONTENTS Significance Test 21 Effect Sizes 22 Micro-Assessment 23 Means 23 Weights 24 Summary of Interpretation Themes 25 Summary of Multivariate Themes 25 3 Background Themes 28 Preliminary Considerations before Multivariate Analyses 28 Data 28 Measurement Scales 29 Roles of Variables 30 Incomplete Information 31 Missing Data . 32 Descriptive Statistics 33 Inferential Statistics 34 Roles of Variables and Choice of Methods 35 Summary of Background Themes 36 Questions to Help Apply Themes to Multivariate Methods 37 II: INTERMEDIATE MULTIVARIATE METHODS WITH 1 CONTINUOUS OUTCOME 4 Multiple Regression 43 Themes Applied to Multiple Regression (MR) What Is MR and How Is It Similar to and Different from Other Methods? 43 When Is MR Used and What Research Questions Can It Address? 44 What Are the Main Multiplicity Themes for MR? 45 What Are the Main Background Themes Applied to MR? 45 What Is the Statistical Model That Is Tested with MR? 46 How Do Central Themes of Variance, Covariance, and Linear Combinations Apply to MR? 47 What Are the Main Themes Needed to Interpret Results at a Macro-Level? 47 What Are the Main Themes Needed to Interpret Results at a Micro-Level? 49 Significance t-Tests for Variables 49 Weights 49 Squared Semipartial Correlations 50 What Are Some Other Considerations or Next Steps After Applying MR? 50 CONTENTS ix What Is an Example of Applying MR to a Research Question? 51 Descriptive Statistics 51 Reliability Coefficients and Correlations 52 Standard Multiple Regression (DV: STAGEB) 52 Hierarchical Multiple Regression (DV: STAGEB) 54 Stepwise Multiple Regression (DV: STAGEB) 56 Summary 61 5 Analysis of Covariance 63 Themes Applied to Analysis of Covariance (ANCOVA) What Is ANCOVA and How Is It Similar to and Different from Other Methods? 63 When is ANCOVA Used and What Research Questions Can it Address? 65 What Are the Main Multiplicity Themes for ANCOVA? 66 What Are the Main Background Themes Applied to ANCOVA? 67 What Is the Statistical Model That Is Tested with ANCOVA? 68 How Do Central Themes of Variance, Covariance, and Linear Combinations Apply to ANCOVA? 69 What Are the Main Themes Needed to Interpret ANCOVA Results at a Macro-Level? 69 Significance Test 70 Effect Size 70 What Are the Main Themes Needed to Interpret ANCOVA results at a Micro-Level? 70 What Are Some Other Considerations or Next Steps After Applying ANCOVA? 71 What Is an Example of Applying ANCOVA to a Research Question? 71 Descriptive Statistics 72 Correlations 73 Test of Homogeneity of Regressions 74 ANOVA and Follow-up Tukey Tests 74 ANCOVA and Follow-up Tukey Tests 77 Summary 80 III: MATRICES 6 Matrices and Multivariate Methods 85 Themes Applied to Matrices What Are Matrices and How Are They Similar to and Different from Other Tools? 85 What Kinds of Matrices Are Commonly Used with Multivariate Methods? 86