LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page iv Aptara Inc. LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page i Aptara Inc. Statistics for Nursing and Allied Health Stacey B. Plichta, ScD Professor of Urban Public Health Hunter College The City University of New York (CUNY) New York, New York Laurel S. Garzon, PhD, PNP Director Graduate Nursing Programs School of Nursing Old Dominion University Norfolk, Virginia LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page ii Aptara Inc. Acquisitions Editor:Hilarie Surrena Managing Editor: Helene T. Caprari Senior Managing Editor / Production:Erika Kors Director of Nursing Production:Helen Ewan Art Director, Design:Holly McLaughlin Art Director, Illustration:Brett MacNaughton Manufacturing Coordinator: Karin Duffield Senior Manufacturing Manager:William Alberti Production Services / Compositor:Aptara, Inc. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please contact Lippincott Williams & Wilkins at 530 Walnut Street, Philadelphia PA 19106, via email at [email protected] via website at lww.com (products and services). 9 8 7 6 5 4 3 2 1 Printed in the United States of America Library of Congress Cataloging-in-Publication Data Plichta, Stacey Beth, 1965- Statistics for nursing and allied health / Stacey B. Plichta, Laurel S. Garzon. p. ; cm. Includes bibliographical references and index. ISBN–13: 978-0-7817-5459-0 ISBN–10: 0-7817-5459-3 1. Nursing—Research—Statistical methods. 2. Medical statistics. I. Garzon, Laurel S. II. Title. [DNLM: 1. Statistics as Topic—methods. 2. Nursing Research. WA 950 P728s 2009] RT68.P65 2009 610.73072—dc22 2008024783 Care has been taken to confirm the accuracy of the information presented and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the contents of the publication. Application of this information in a particular situation remains the professional responsibility of the practitioner; the clinical treatments described and recommended may not be considered absolute and universal recommendations. The authors, editors, and publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accordance with the current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new or infrequently employed drug. Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It is the responsibility of the health care provider to ascertain the FDA status of each drug or device planned for use in his or her clinical practice. LWW.COM LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page iii Aptara Inc. Dedications I would like to dedicate this book to my family for all of the love and support that they have given me, especially to my mother, Patricia Plichta, my husband, Bill Kellar, and my children, Jesse Carroll and Samantha Lee. I would also like to thank all of my graduate students, who over the years have helped to shape this book. I would like to give special thanks to two of my former students, Dr. Yan Zhang and Mr. Paul Magnant, who spent many hours reading drafts, developing homework exercises, and making this book more accessible to students. My thanks also extend to another former student, YuQuin Zhao, who provided a diligent and thorough review of our earlier drafts. Finally, I would like to thank the editors at LWW, notably Helene Caprari, Michelle Clarke, and Margaret Zuccarini, who with much patience and support have seen this project through to completion. Stacey B. Plichta I would like to thank Beth and Anna for their love and Dot for my strength. Laurel S. Garzon LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page iv Aptara Inc. LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page v Aptara Inc. Reviewer List Noori Akhtar-Danesh, MSc, PhD Willa Marlene Doswell, PhD, RN, FAAN Assistant Professor Associate Professor McMaster University University of Pittsburgh School of Nursing Hamilton, Canada Pittsburgh, Pennsylvania Gina S. Brown, PhD, RN Mary Beth Flanders, PhD, RN Professor and Chair Associate Professor Edyth T. James Department of Nursing Fay Whitney School of Nursing Columbia Union College University of Wyoming Takoma Park, Maryland Laramie, Wyoming Bruce A. Cooper, PhD David Anthony Forrester, PhD, RN Senior Statistician Professor Associate Adjunct Professor University of Medicine and Dentistry of New University of California Jersey San Francisco, California Newark, New Jersey Marcus Davey, PhD Simon Geletta, PhD Assistant Research Professor Assistant Professor Department of Surgery Des Moines University Assistant Course Director Des Moines, Iowa School of Nursing University of Pennsylvania Beth S. Hembree, RN, MSN, DSN Philadelphia, Pennsylvania Professor Director of Graduate Studies Rose Ann DiMaria-Ghalili, PhD, RN, CNSN Lurleen B. Wallace College of Nursing Associate Professor Jacksonville State University West Virginia University Jacksonville, Alabama Morgantown, West Virginia LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page vi Aptara Inc. vi Reviewer List James E. Hodge, EdD Patsy L. Ruchala, DNSc, RN Professor of Mathematics Director Mountain State University Orvis School of Nursing Beckley, West Virginia University of Nevada Reno, Nevada Ezra C. Holston, PhD, MSN, RN Assistant Professor Cynthia L. Russell, PhD, RN University of California Assistant Professor Los Angeles, California University of Missouri-Columbia Sinclair School of Nursing Ann F. Jacobson, PhD, RN Columbia, Missouri Associate Professor Kent State University College of Nursing Mina D. Singh, RN, PhD Kent, Ohio Assistant Professor York University Tae Sook Kim, PhD Toronto, Canada Associate Professor Saint Joseph’s College Ida L. Slusher, RN, DSN Brooklyn, New York Professor Eastern Kentucky University Rosalie O. Mainous, PhD, ARNP Richmond, Kentucky Acting Associate Dean for Academic Affairs University of Louisville Sandra L. Smith, PhD, APRN Louisville, Kentucky Assistant Professor University of Utah Margaret E. Miller, PhD Salt Lake City, Utah Professor of Nursing Bellarmine University Darlene Steven, MHSA, PhD, PHN, RN Louisville, Kentucky Professor and Coordinator Lakehead University Catherine Pearsall, PhDc, FNP, RN Thunder Bay, Canada Assistant Professor Saint Joseph’s College Jessica L. Thomson, PhD Patchogue, New York Statistician, Adjunct Professor Louisiana State University Health Sciences Michael Perlow, DNS, RN Center Professor of Nursing Baton Rouge, Louisiana Murray State University Murray, Kentucky Karen S. Ward, PhD, RN, COI Professor and Associate Director of Online Marjorie A. Pett, MStat, DSW Programs Research Professor Middle Tennessee State University University of Utah College of Nursing Murfreesboro, Tennessee Salt Lake City, Utah Sarah Ransdell, PhD Associate Professor Nova Southeastern University Fort Lauderdale, Florida LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page vii Aptara Inc. Preface Statistical analysis is an important tool in the conduct of clinical, basic, and out- comes research in nursing and allied health. Nurses and allied health providers with a focus on practice are best qualified to identify and develop research that affects the delivery of care and patient outcomes. Current concerns about the cost, quality, and equitable delivery (i.e., among all racial and ethnic groups) of health care can be addressed by evidenced-based practices with measurable out- comes of care. Evidence-based practice is a process by which systematic inquiry is used to explain or answer questions of interest. Research provides a process for careful, organized, and thoughtful analysis and consideration of myriad evolving prob- lems. Health care issues require an ongoing review and analysis of the congru- ency of financial issues, personnel issues, methods of care, and outcomes. A systematic research approach includes a step-by-step process of identifying a problem or question, selecting the relevant variables, and then using the most appropriate statistical method. This process can overwhelm beginners, but approaching a research project in an organized way with the knowledge of the basic statistics provided in this text can lead to a new and exciting understanding of how powerful statistics can be. The choice of a particular statistical method depends on the type of question asked (e.g., Are two or more things being com- pared?), the variables selected (e.g., What are the important components of the problem?), the level of measurement of the variables (e.g., What types of instru- ments will be used?), and the level of certainty that is required. This text takes the reader through this process. Readers will learn the language of statistics, how to organize the data, and how to describe the data with simple statistics. This text provides a good beginning to understand what data can reveal about research. LWBK083-3844G-FM_pi-xii.qxd 7/7/08 10:39 AM Page viii Aptara Inc. viii Preface DEVELOPING RESEARCH AND STATISTICAL METHODS Nursing research began in Florence Nightingale’s Notes of Nursing (1859). She described the factors that she believed affected the outcomes of soldiers in the Crimean war in a systematic way. Her notes provided the basis for a review of the care these soldiers received, which, in turn, stimulated changes in nursing care and public health. Much of the research in the decades to follow was research about the education of nurses. Sigma Theta Tau, the International Honor Society of Nursing, became the first organization to fund nursing research in the United States, awarding a research grant in 1936. In the 1930s, the American Journal of Nursingbegan pub- lishing nursing research studies. In 1952, Nursing Researchwas created to share the developing body of nursing studies. Today, this journal enjoys an international rep- utation for being the foremost journal for peer-reviewed nursing research. In the 1970s, the focus of research changed to the investigation of nursing practice and the outcomes of nursing. The increased rigor required to investigate practice-related issues required an in-depth knowledge of research design and sta- tistical methods. Peer review was required for publication as additional journals, such as Research in Nursing and Health and Advances in Nursing Science, were developed to publish these studies. Clinical problems and issues related to practice were identified as the foremost need for nursing research (Lindeman, 1975). In 1986, the importance of nursing research was recognized with the estab- lishment of the National Center for Nursing Research (NCNR), which is part of the National Institutes of Health. This center provides funding for nursing research and trains nurse researchers. The selection for funding developed into a rigorous peer-reviewed process in which the design and statistical methods of research projects are carefully reviewed. The funding provided by the NCNR has grown to over $150 million annually. Current trends in nursing research are focused on evidenced-based practice (Huddleston, Berkheimer, Landis, et al., 2005; McCormick, Naimark, and Tate, 2006), increased rigor of studies (Im, Page, Lin, Tsai, and Cheng, 2004; Sterling and Peterson, 2005), multidisciplinary research, more visibility for nursing research, and a focus on culture and health disparities (Peragallo, DeForge, O’Campo, et al., 2005). ORGANIZATION OF THE CONTENT The Role of Research in Health Care In Chapter 1, “Using Research and Statistics in Health Care,” the role of research in health care is explored. Research in nursing and allied health has contributed