TECHNICAL REPORT | JUNE 2014 Development of the ATOS® Readability Formula Written for Renaissance Learning® by Michael Milone, Ph.D. Introduction by Dr. Andrew Biemiller, Professor Emeritus, University of Toronto © 2014 by Renaissance Learning, Inc. All rights reserved. Printed in the United States of America. All logos, designs, and brand names for Renaissance’s products and services, including but not limited Accelerated Reader, AR, ATOS, Renaissance, Renaissance Learning, and Star Reading, are trademarks of Renaissance. This publication is protected by U.S. and international copyright laws. It is unlawful to duplicate or reproduce any copyrighted material without authorization from the copyright holder. For more information, contact: Renaissance P.O. Box 8036 Wisconsin Rapids, WI 54495-8036 (800) 338-4204 www.renaissance.com
[email protected] 06/14 ©Copyright 2014 Renaissance Learning, Inc. All rights reserved. 2 Contents 4 Introduction by Dr. Andrew Biemiller, Professor Emeritus, University of Toronto 7 Overview of the ATOS® Readability Formula 7 Readability and its importance 9 Evolution of readability measures 10 Developing the ATOS® Readability Formula 15 Adjustments to ATOS® 16 Refinements to ATOS®—2013 17 The Graded Vocabulary List 22 Alternate scale for ATOS® 22 Conclusion Appendices 23 Appendix A: Studies of factors thought to affect readability 36 Appendix B: Accelerated Reader® Goal-Setting Chart 37 References Tables 13 Table 1. Correlation of semantic and syntactic variables to text difficulty 13 Table 2. Types of transformations 14 Table 3. Squared correlations of the best predictors with each of the selected six transformations 21 Table 4. Examples of grade assignments for derivative forms of base words 23 Table A1.