Bacharach Verne R. - Psychometrics: An Introduction

Psychometrics

Second Edition

Michael Furr dedicates this book to his Mother and Father.
Verne Bacharach dedicates this book to his children,
Leigh, Sam, and Will, and to their Mothers.

An Introduction

Second Edition

R. Michael Furr

Wake Forest University

Verne R. Bacharach

Appalachian State University

FOR INFORMATION:

SAGE Publications, Inc.
2455 Teller Road
Thousand Oaks, California 91320
E-mail:

SAGE Publications Ltd.
1 Olivers Yard
55 City Road
London, EC1Y 1SP
United Kingdom

SAGE Publications India Pvt. Ltd.
B 1/I 1 Mohan Cooperative Industrial Area
Mathura Road, New Delhi 110 044
India

SAGE Publications Asia-Pacific Pte. Ltd.
3 Church Street
#10-04 Samsung Hub
Singapore 049483

Acquisitions Editor: Reid Hester
Associate Editor: Eve Oettinger
Editorial Assistant: Sarita Sarak
Production Editor: Eric Garner
Copy Editor: QuADS Prepress (P) Ltd.
Typesetter: Hurix Systems Pvt. Ltd.
Proofreader: Laura Webb
Indexer: Marilyn Augst
Cover Designer: Edgar Abarca
Marketing Manager: Lisa Sheldon Brown
Permissions Editor: Karen Ehrmann

Copyright 2014 by SAGE Publications, Inc.

All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher.

Printed in the United States of America

A catalog record of this book is available from the Library of Congress.

978-1-4522-5680-1

This book is printed on acid-free paper.

13 14 15 16 17 10 9 8 7 6 5 4 3 2 1

M easurement is at the heart of all science and of all applications of science. This is true for all areas of science, including the scientific attempt to understand or predict human behavior. Behavioral research, whether done by educators, psychologists, or other social scientists, depends on successful measurement of human behavior or of psychological attributes that are thought to affect that behavior. Likewise, the application of psychological or educational science often rests on successful measurement at a level that is no less important than it is in research. Indeed, scientifically sound clinical or educational programs and interventions require measurement of the behaviors or psychological attributes of the individuals enrolled in these programs.

This book is concerned with methods used to evaluate the quality of measures, such as psychological tests, that are used in research and applied settings by psychologists and others interested in human behavior. The scientific study of the quality of psychological measures is called psychometrics. Psychometrics is an extremely important field of study, and it can be highly technical. In fact, an article published in the New York Times (Herszenhorn, 2006) stated that psychometrics, one of the most obscure, esoteric and cerebral professions in America, is also one of the hottest.

Despite the potential esoteric and cerebral nature of the field, psychometrics does not need to be presented in a highly technical manner. The purpose of our book is to introduce the fundamentals of psychometrics to people who need to understand the properties of measures used in psychology and other behavioral sciences. More specifically, our goal is to make these important issues as accessible and as clear as possible, to as many readers as possibleincluding people who might initially shy away from something that might be seen as obscure, esoteric, and cerebral.

With these goals in mind, our coverage of psychometrics is intended to be deep but intuitive and relatively nontechnical. We believe that this is a novel approach. On one hand, our treatment is much broader and deeper than the cursory treatment of psychometrics in undergraduate Tests and Measurement texts. On the other hand, it is more intuitive and conceptual than the highly technical treatment in books and journal articles intended for use by professionals in the field of psychometrics. We believe that anyone familiar with basic algebra and something equivalent to an undergraduate course in statistics will be comfortable with most of the material in this book. In general, our hope is that readers will attain a solid and intuitive understanding of the importance, meaning, and evaluation of a variety of fundamental psychometric concepts and issues.

This book is highly relevant for a variety of courses, including Psychological Testing, Psychometrics, Educational Measurement, Personality Assessment, Cognitive Assessment, Clinical Assessment, and, frankly, any type of Assessment course. Moreover, it could be an important part of courses with an emphasis on measurement in many areas of basic and applied sciencefor example, in medical training, sociology, exercise science, and public health.

Thus, this book is intended for use by advanced undergraduates, graduate students, and professionals across a variety of behavioral sciences and related disciplines. It will be of value to those who need a solid foundation in the basic concepts and logic of psychometrics or measurement more generally. Although it was not primarily written for people who are intending to become or already are psychometricians, it can serve as a very useful complement to the more technical texts.

In our attempt to make the topics of psychometrics accessible to our target audience, we constructed illustrative testing situations along with small artificial data sets to demonstrate important features of psychometric concepts. The data sets are used alongside algebraic proofs as a way of underscoring the conceptual meaning of fundamental psychometric concepts. In addition, we have departed from the usual practice of having a separate chapter devoted to statistics. Instead, we introduce statistical concepts throughout the text as needed, and we present them as tools to help solve particular psychometric problems. For example, we discuss factor analysis initially in the context of exploring the dimensionality of a test. Thus, we tie the statistical procedures to a set of important and intuitive conceptual issues. Our experience as classroom instructors has taught us that students benefit when quantitative concepts are linked to problems in this way, as the links seem to reinforce students understanding of both the statistical procedures and the psychometric concepts.

The organization of this book is intended to facilitate the readers insight into core psychometric concepts and perspectives. In the first chapter, we address the basic importance of psychological measurement and psychometrics. In addition, we examine a few important issues and themes that cut across all remaining chapters. This explicit treatment of these issues and themes should help solidify the concepts that are addressed in the later chapters.

In , we address important issues in measurement theory and in the statistical basis of psychometric theory. These chapters are fundamental to a full appreciation and understanding of the later chapters that examine psychometric theory in depth. Specifically, these chapters examine issues of scaling in psychological measurement, concepts in the quantification of psychological differences and the quantification of associations among psychological variables, issues in the interpretation of test scores, and concepts in the meaning and evaluation of test dimensionality. Although these topics can be technical, our intention is to focus these chapters at a level that is relatively intuitive and conceptual.