INTRODUCTION TO NUTRITION AND HEALTH RESEARCH

INTRODUCTION TO NUTRITION AND HEALTH RESEARCH

by

Eunsook T. Koh

and

Willis L. Owen

University of Oklahoma Health Sciences Center

SPRINGER SCIENCE+BUSINESS MEDIA, LLC

... " Electronic Services <http://www.wkap.nl>

Library of Congress Cataloging-in-Publication Data Koh, Eunsook T.

Introduction to nutrition and health research / by Eunsook T. Koh and Willis L. Owen. p. ;cm.

Includes bibliographical references and index. ISBN 978-1-4613-5535-9 ISBN 978-1-4615-1401-5 (eBook) DOI 10.1007/978-1-4615-1401-5 1. Health-Research-Methodology. 2. Nutrition-Research-Statistical methods. 1.

Owen, Willis L. II. Title. [DNLM: 1. Nutrition. 2. Research-methods. 3. Research Design. 4.

Statistics-methods. 5. Writing. QU 145 K787i 2000] RA645.N87 K64 2000 610' .7'2-dc21

00-061056

Copyright «>2000 Springer Science+Business Media New York Originally published by Kluwer Academic Publishers in 2000 Softcover reprint of the hardcover 1 si edition 2000 Ali rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, mechanical, photo­copying, recording, or otherwise, without the prior written permission of the publisher, Springer Science+Business Media, LLC.

Printed an acid-free paper.

The Publisher offers discounts on this bookfor course use and bulk purchases. For further information, send email to<david.cella@wkap.com> .

CONTENTS

Preface xiii

Acknowledgements xv

Part I Overview of the Research Process 1

Chapter 1. Introduction to Research in Nutrition and Health 2

Definition of Research 2 Types of Research 3 Basic and Applied Research 3 Field versus Laboratory Research 3 Qualitative, Descriptive and Experimental Research 4 Unscientific and Scientific Methods of Problem Solving 5 The Rationalistic Method 6 The Empirical Method 6 The Scientific Method of Problem Solving 7 Summary 10 References 11

Chapter 2. Research Problem and Literature Review 13

Introduction 13 Identifying the Research Problem 13 Using Inductive and Deductive Reasoning 14 Purposes of the Literature Review 16 Primary and Secondary References 16 Reading and Recording the Literature 19 Critically Evaluating the Literature 21 Writing the Literature Review 22 Summary 23 References 25

vi

Chapter 3. Framing a Research Problem: Hypotheses, Purposes, Objectives, and Questions 27

Choosing the Title 27 Writing the Introduction 29 Framing a Research Problem 33 Stating the Research Problem 34 Identifying the Variables 34 Hypotheses 36 Operational Definitions 37 Outlining Basic Assumptions, Limitations, Delimitations 37 Summary 39 References 40

Chapter 4. Writing Method Sections 41

Planning the Work 41 Describing Subjects 42 Subjects Sources and Selections 44 Diet and Other Interventions 48 Describing Instruments 49 Describing Procedures 49 Describing Design and Analysis 50 Statistical Analysis 50 Summary 54 References 55

Chapter 5. Ethical Issues in Research and Scholarship 57

Introduction 57 Misconduct in Science 57 Plagiarism 58 Fabrication and Falsification 59 Misleading Authorship 60 Ethical Issues Regarding Copyright 62 Protecting Human Subjects 63 Components of an Informed Consent 66 Guidelines for Using Human Subjects in Writing

Proposals to the National Institutes of Health 67 Protecting Animal Subjects 68

vii

Guidelines for Using Animals in Research Proposals to the National Institutes of Health 68

Institutional Animal Care and Use Committee 69 Summary 69 References 70

Part II. Statistical and Measurement Concepts in Research 73

Chapter 6. Statistical Concepts 74

Introduction 74 Applications of Statistics in Research 75 Levels of Measurements 78 Descriptive and Inferential Statistics 79 Sample Selection 80 Central Tendency 82 Two Categories of Statistical Tests: Parametric and

Nonparametric Statistics 85 The Standard Normal Distribution 86 Application of the Normal Curve 90 The Normal Distribution as a Probability Curve 92 Hypothesis Testing 93 Null and Alternative Hypotheses 94 Two-Tailed versus One-Tailed Hypothesis Tests 94 Alpha (Type I error) 94 Beta (Type II error) 95 Meaningfulness (Effect Size) 96 Determining Required Sample Size 97 Summary 98 References 101

Chapter 7. Relationships Among Variables 103

Introduction: Correlation and Regression 103 Types of Relationships Between Two Variables 104 Applications of Correlation and Regression in Research 105 How Correlation Research Investigates 107 Correlation Coefficient 111 What the Coefficient of Correlation Means 112

viii

Using Correlation for Prediction (Regression) 115 Interpreting Meaningfulness of r 118 Standard Error of Estimate 118 Partial Correlation 121 Multiple Regression Prediction Equation 121 Summary 123 References 125

Chapter 8. Differences Among Groups 127

Introduction 127 How Statistics Test Differences 127 Three Types of Student's t Test 128 Estimating Meaningfulness of Treatments 131 t Tests and Power in Research 135 Analysis of Variance: One way of ANOV A 136 Characteristics of the F Distribution 137 Follow-up Testing 140 Factorial Analysis: Two-Way of ANOVA 141 Analysis of Covariance 151 Summary 152 References 153

Chapter 9. Nonparametric Statistics 155

Introduction 155 Chi-square 156 Spearman Rank Correlation Coefficient 162 Mann-Whitney-Wilcoxon Test 165 Wilcoxon Matched-Pair Signed Ranks Test 165 Kruskal-Wallis ANOV A 166 Friedman's ANOVA 166 Summary 166 References 168

Chapter 10. Measuring Research Variables 169

Introduction 169 Comparisons of Scales: Practical Considerations and Statistics 169 Reliability 171 Precision and Accuracy 173

ix

Validity 175 Measurement Errors in Dietary Assessment 177 Assessment and Control of Measurement Errors 179 Error Sources 180 Precision in Dietary Assessment 181 Validity in Dietary Assessment Methods 183 Use of Biochemical Markers to Validate Dietary Data 186 Anthropometric Assessment 188 Clinical Assessment 189 Summary 189 References 191

Part III Various Types of Research 195

Chapter 11. Experimental and Quasi-Experimental Research 196

Introduction 196 Internal and External Validity 197 Controlling Threats to Internal Validity 204 Controlling Threats to External Validity 206 Pre-Experimental Designs 207 True Experimental Designs 207 Randomized-Groups Design 208 Pretest-Posttest Randomized-Groups Design 210 Factorial Design 210 Solomon Four-Group Design 211 Quasi-Experimental Designs 213 Summary 215 References 216

Chapter 12. Descriptive Research and Qualitative Research 219

Definition of Descriptive Study 219 Definition of Qualitative Research 219 Survey Research 220 Questionnaires 220 Personal Interview 226 The Delphi Method 228 The Normative Survey 228

x

Nutrition Survey 228 Dietary Intake 229 Epidemiologic Descriptive Survey 232 Epidemiologic Approaches to Diet and Disease 232 Correlation Studies 233 Special Exposure Groups 234 Migrant Studies and Secular Trends 234 Case-Control studies 235 Cohort Studies 235 Controlled Trials 236 Cross Sectional Study 237 Meta-Analysis and Pooled Analysis 238 Qualitative Research 239 Summary 242 References 244

Part IV. Writing the Research Proposal and Results 249

Chapter 13. Results, Discussion, and Abstract 250

Introduction 250 Use of Tables in Data Presentation 251 Use of Graphs in Data Presentation 254 The Histogram 256 The Bar Graph 257 The Pie Chart 259 The Scatter Diagram 260 Photographs 263 Uniform Requirements for Manuscripts 265 Discussion 267 Abstract 269 Report of Qualitative Study 272 Summary 272 References 274

Chapter 14. Publications 277

Research Report 277 Thesis or Dissertation Writing Guidelines 277 Limitations of Chapter Style 278

Preliminaries Body of the Thesis or Dissertation Presentations and Manuscripts Oral Presentations Poster Presentations Manuscripts Author's Guidelines: Submitting the Article Summary References

Chapter 15. Writing the Research Proposal

Introduction Identifying the Research Problem Choosing the Topic Formulating the Hypotheses Developing the Research Protocol Abstract Specific Aims Background and Significance Preliminary Studies/Progress Report Research Design and Methods Why Grant Proposal Fail Suggestions for Grant Writing How to Prepare a Strong Proposal Summary References

Part V. Using Computers in Research

Chapter 16. Using Computers

Introduction Hardware Software Data Entry Software Graphical Software Statistical Software Data Analysis Examples Summary Statistics

279 283 288 288 290 291 292 292 293 295

299

299 299 300 300 301 302 302 303 303 304 305 305 306 307 308

309

310

310 310 312 312 313 313 314 315

xi

xii

A simple Histogram 320 A t test for independent groups 321 Analysis of a Contingency Table 323 Calculation of Correlation Coefficients 326 Simple Linear Regression 330 Multiple Regression 331 One Way Analysis of Variance without Repeated Measures 333 Two Factor Analysis of Variance for Independent Groups 335 Single Factor Analysis of Variance with Repeated Measures 336 Two Factor Analysis of Variance with Repeated Measures 339 Summary 341 References 342

Appendix 343

A. Statistical Tables 343

Subject Index 358

Preface

A course on dietetics, nutrition and health research methods is generally one of the first courses both theses and non-theses students should take. Nonetheless, during the several years that we have taught the course "Research Methods in Dietetics, Nutrition and Health," we have not found any textbook on this critical topic. This book will hopefully fill the gap in dietetics, nutrition, and health educational literature.

This book is based on the research methods its authors have used to teach master's degree level introductory courses on dietetics, nutrition and health research methods as well as the feedback from the students in those courses. The primary objectives of the authors' courses are to teach students how to conduct their own research and how to understand the research of others. This book shares the same objectives and strives to be comprehensive yet still practical and understandable. This book is designed to help students create their own research projects and write their masters' theses as well as to teach students who will not write masters' theses how to analyze and interpret research articles. The book includes many refereed nutrition and medical journal articles so that students can learn how researchers identified research problems; how they framed the problems; how they planned and conducted research to address the problem; and how they reported, interpreted, and implemented their findings through real articles.

Doctoral students and beginning researchers who want an overview of the research process should find this book helpful. However, the procedures and techniques specific to a certain type of research in a specialized area are not covered in this book.

The growth of our professions depends upon being active producers and/or consumers of research. Researchers, teachers, technicians, and counselors need to understand the research process. I believe this book provides the necessary information for both the consumer and the producer of research.

Part I (Chapters 1-5) of the book provides a complete overview of the research process: developing a research topic, reviewing current literature on the topic, selecting a research approach, writing a prospectus, and analyzing the ethical issues in research and scholarship.

Part II (Chapters 6-10) discusses statistical and measurement concepts in research such as descriptive versus inferential statistics, parametric versus non-parametric procedures, and measurement issues associated with

xiv

dependent variables. Part II is designed for students with no background in statistics and limited backgrounds in mathematics.

Part III (Chapters 11 and 12) explores the various types of research: experimental, quasi-experimental, descriptive, and qualitative research. This section also explains the various types of experimental designs.

Part N (Chapters 13-15) explains how to present research results via oral and poster presentations, and how to write theses, dissertations, journal articles and research proposals.

Part V (Chapter 16) highlights the use of computers in research and demonstrates the various ways of data analysis.

Acknowledgments

This book is the product of many minds. Great appreciation is extended to Dr. Richard G. Allison, Executive Officer of the American Society for Nutritional Sciences for his supports and encouragement for me to complete this book.

Professor Judith C. Wilkerson and Mrs. Annette Moss have provided invaluable comments that have greatly improved the book. We have also striven to incorporate the astute feedback from our "Research Methods in Dietetics, Nutrition and Health" students on how this subject should be taught.

Thanks must be expressed to faculty and staff members in the Department and College who helped us to complete the book manuscript, especially, Gina R. Vile for her invaluable efforts in preparing the text and illustrations; and Gaylon E. Bright for his computer skills. The authors are very grateful to staff members, especially, Tony B. Cable and Michael Sweezy, in the Printing Services, Health Sciences Center, for their art works. This text would not have been possible without their contribution.

Finally, the authors wish to express their sincere thanks to Joanne Tracy, the Editor-in-Bio-sciences at Kluwer Academic Publishers, who gave essential support and counsel during the production of the book, and the editorial assistant, Mary Panarelli, for her technical advice and supports.

Eunsook T. Koh

Willis L. Owen

Needless to say, countless hours were expended by the co-author, Dr Willis L. Owen, to write Chapter 16 and to review all other chapters. Without his careful evaluation the present book would not have been possible.

Eunsook T. Koh