A Comparability Study On The Lexical Complexity Of CET-6,IELTS And TOEFL IBT Reading Tests

CET-6,IELTS and TOEFL iBT are all large-scale and high-stakes English language tests.Although the three tests vary in their purpose,structure,and score interpretation,they are comparable in that they can all be used as English language proficiency proof for college admission(within the validity period).Reading is one of the most important skills in second or foreign language learning as well as assessment,for example,CET-6,IELTS and TOEFL iBT.Reading researchers have long been on the journey to unveil contributors to better reading comprehension,and vocabulary is one of the most important contributors to reading comprehension.Therefore,lexical task demand or lexical complexity is regarded as one important aspect of textual parameters that are related to reading difficulty,and is incorporated in many influential test validation frameworks and language proficiency scales.Regarding these,this study aims to compare the lexical complexity of CET-6,IELTS and TOEFL iBT reading tests by using an online text analyzing tool – Text Inspector.The following research questions guide the whole thesis: 1)What is the lexical complexity for the reading texts of CET-6,IELTS and TOEFL iBT reading tests? 2)What are the similarities and differences among the lexical complexity for the texts of the three reading tests? In this paper,the lexical complexity is measured from lexical difficulty and lexical diversity.The measures for lexical difficulty include the average syllable numbers per 100 words,BNC LFC(token),BNC LFC(type),COCA LFC(token)and COCA LFC(type),while the measures for lexical diversity include VOCD and MTLD.From lexical difficulty and diversity,the major findings of the current study are summarized as follows:(1)The lexical difficulty of the three tests is all comparatively high and belongs to the academic texts,though with some lower and higher outliers.The TOEFL iBT has the highest lexical difficulty and CET-6 has the lowest.Except BNC LFC data,all other measures are statistically significantly different from each other.(2)The lexical diversity of CET-6 is comparatively high and more diversified than the norm of academic texts that was established by previous research,though with some outliers,and this is also true for IELTS.But the vocabulary used in TOEFL iBT reading test passages is not that diversified,with quite some of the articles below the norm.It is worth mentioning that TOEFL iBT enjoys a higher reliability of lexical diversity despite some outliers.The measures of lexical diversity of show that CET-6 has the most diversified vocabulary,while the TOEFL iBT that has the highest lexical difficulty scores has the lowest lexical diversity.The significance tests show that the three tests are significantly different from each other in terms of lexical diversity.Based on the findings,this study can provide empirical evidence for the test comparability of CET-6,IELTS and TOEFL iBT by focusing on lexical complexity.It is of value in four aspects.First,it can provide empirical evidence for the content validity of the three tests' reading section,on which meaningful inferences of candidates' reading abilities from the tests scores can be based.Second,students and teachers of test preparation courses can be informed of the similarities and differences of the three tests,which benefits their learning and teaching for the three tests.Third,problems of the tests may be detected,which will call for testing institutions' and test designers' attention and facilitate their endeavors to enhance the quality and validity of the tests.Lastly,this study will enrich the field-relevant studies for test comparability studies and offer both a theoretical and methodological paradigm for future research.