University of Central Florida STARS Electronic Theses and Dissertations, 2004-2019 2013 The Intricate Relationship Between Measures Of Vocabulary Size And Lexical Diversity As Evidenced In Non-native And Native Speaker Academic Compositions Melanie Gonzalez University of Central Florida Part of the Education Commons Find similar works at: https://stars.library.ucf.edu/etd University of Central Florida Libraries http://library.ucf.edu This Doctoral Dissertation (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2004-2019 by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Gonzalez, Melanie, "The Intricate Relationship Between Measures Of Vocabulary Size And Lexical Diversity As Evidenced In Non-native And Native Speaker Academic Compositions" (2013). Electronic Theses and Dissertations, 2004-2019. 2633. https://stars.library.ucf.edu/etd/2633 THE INTRICATE RELATIONSHIP BETWEEN MEASURES OF VOCABULARY SIZE AND LEXICAL DIVERSITY AS EVIDENCED IN NON-NATIVE AND NATIVE SPEAKER ACADEMIC COMPOSITIONS by MELANIE C. GONZÁLEZ B.A. University of Central Florida, 2003 M.A. University of Central Florida, 2007 A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Education and Human Performance at the University of Central Florida Orlando, Florida Summer Term 2013 Major Advisor: Keith S. Folse ABSTRACT The present study, a quantitative lexical analysis, examines the extent to which vocabulary size and lexical diversity contribute to writing scores on advanced non-native speakers’ and native speakers’ academic compositions. The data consists of essays composed by 104 adult non-native English learners enrolled in advanced second language writing courses and 68 native speaking university students in a first-year composition course. The lexical diversity of the sample essays is quantified by both the Measure of Textual Lexical Diversity (MTLD) and the voc-D while vocabulary size is measured by CELEX word frequency means, three instruments that are available in the computational linguistics program Coh-Metrix 3.0. Writing scores are provided by three independent raters’ evaluations according to the TOEFL iBT Independent Writing Rubric. Results from a binary logistic regression reveal that lexical diversity has a significantly greater impact on writing score than vocabulary size (p < .01). Nevertheless, a series of MANOVAs indicate that vocabulary size initially facilitates writing scores at the lower proficiency levels, but it is an essay’s lexical diversity that promotes it to the higher score levels. Additional findings from the MANOVAs demonstrate that native speakers’ profiles of lexical diversity and size are significantly different from their non-native peers (p < .001). The lexical profiles also differed significantly among the individual score levels of the TOEFL iBT rubric (p < .05). A final outcome from a Pearson’s product moment correlation analysis shows that ii vocabulary size has only a moderate relationship to lexical diversity, suggesting that variation of mid-range vocabulary may be more important to writing proficiency than the use of more sophisticated terms that occur less frequently in natural language. Implications for practice suggest that it is not enough to simply teach vocabulary words in the L2 composition classroom, but also to guide learners in how to employ these words in a varied manner within their writing. Furthermore, the results of this study indicate that teachers should spend more time on helping students use medium frequency words along with synonyms of a similar frequency rather than teaching students infrequent vocabulary, which may appear to sound more advanced. iii ACKNOWLEDGMENTS As this rite of Ph.D passage comes to a close, there are many people who readily and kindly contributed to not just this study, but also my doctoral program and overall well being through these past few years. First and foremost, my sincerest and heartfelt gratitude goes to Dr. Keith Folse for his unwavering support, guidance, and encouragement that truly helped me see this study through to its end. His absolute faith in my capabilities as a burgeoning researcher and professor truly warmed my heart. Dr. Folse’s resolute dedication to the field and to his students is a source of never-ending inspiration for me. I could not have dreamed of a better mentor. I am immensely grateful to Dr. Stuart Webb who challenged me to think of my research questions in multiple ways. Many aspects of this study were inspired by his research, and I feel truly honored for his service on this committee. I am fortunate to have had his direction in the formulation of this study. Additionally, I must also send a huge thanks to Dr. Haiyan Bai and Dr. Florin Mihai for their integral membership in my dissertation committee. Dr. Bai’s patient guidance as I maneuvered through the multiple statistical analyses aided me to problem- solve in order to find the best possible research design for my data. Likewise, I am very much grateful for Dr. Mihai’s practical advice and assessment expertise without which this study could have been far more complicated than it needed to be. iv I also would like to thank the many instructors and administrators who allowed for me to collect student essays from their institutions. The 183 learners themselves also deserve recognition and thanks for freely allowing me to use their written work for this study. Without their eager participation, this study would not have been possible. Next, I must express my sincerest gratitude to the three raters who graciously volunteered their time to grade essays that were not even composed by their own students! It is no easy feat to evaluate and score so many essays, and they did not hesitate to agree to the task. I am truly humbled by their service and contribution of a most vital part of this study. A special thanks goes to Alison Youngblood, my partner in doctoral student “crime” and biggest champion. It all started with an email inquiring, “are you going to do the Ph.D program?” Her vivacious nature, friendship, and sense of humor helped to carry me through this program. Most of all, I must thank her for always having my back when challenges arose. My most earnest thanks are for my family and friends’ loving support, patience, and delivery of the occasional humorous Internet meme that kept my spirits bright. They forgave and stuck by me for all the times I had to sacrifice precious time with them in order to do something related to my studies, and for that, I am eternally grateful. Of this important group of people in my life, I first thank my husband, Matt Kantrowitz, for being my greatest supporter and source of comfort. He never wavered in expressing his pride and conviction that I would succeed in my doctoral study efforts. Additionally, I v must thank him for the all-important reminders to take breaks from my marathon study and writing sessions! To my parents, Vicente Gonzalez and Jeany Todd Gonzalez, and my sister, Janelle, no words ever seem perfect enough to express my gratitude for their unconditional love and support. Their cheers have been the loudest whenever I experienced both achievements and doubts. They are truly anchors in my life. A final thanks is reserved for my two dachshunds, Charlie and Sammie. They warmed my lap for many of the long hours in front a computer or a book. They were the most loyal friends and never failed to offer their companionship during this program and my life. They are forever in my heart. vi TABLE OF CONTENTS LIST OF FIGURES .............................................................................................................x LIST OF TABLES ............................................................................................................. xi LIST OF ACRONYMS ................................................................................................... xiii CHAPTER 1: INTRODUCTION ........................................................................................1 Background ..................................................................................................................... 4 Rationale ......................................................................................................................... 6 Research Questions ....................................................................................................... 11 Hypotheses .................................................................................................................... 12 Significance of the Study .............................................................................................. 14 Study Limitations .......................................................................................................... 16 Study Assumptions ....................................................................................................... 17 Definitions of Terms for the Study ............................................................................... 18 Organization of the Study ............................................................................................. 20 CHAPTER 2: RESEARCH AND LITERATURE REVIEW ...........................................22 Defining Academic Language ...................................................................................... 23 BICS and CALP .......................................................................................................