Log-likelihood and odds ratio: Keyness statistics for different purposes of keyword analysis
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Publication Details
Author list: Pojanapunya P., Todd R.W.
Publisher: De Gruyter Mouton
Publication year: 2018
Volume number: 14
Issue number: 1
Start page: 133
End page: 167
Number of pages: 35
ISSN: 1613-7027
eISSN: 1613-7027
Languages: English-Great Britain (EN-GB)
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Abstract
Keyword analysis is used in a range of sub-disciplines of applied linguistics from genre analyses to critically-oriented studies for different purposes ranging from producing a general characterization of a genre to identifying text-specific ideological issues. This study compares the use of log-likelihood (LL), a probability statistic, and odds ratio (OR), an effect size statistic, for keyword identification and argues that the two methods produce different keywords applicable to research focusing on different purposes. Through two case studies, keyword analyses of advance fee scams against the British National Corpus and research articles in applied linguistics against research articles from other academic disciplines, we show that both the LL and OR keywords concern the aboutness of the corpus, but differ in their specificity and pervasiveness through the corpus. LL highlights words which are relatively common in general use serving genre purposes, whereas OR highlights more specialized words serving critically-oriented purposes. Methodological and practical contributions to keyword analysis are discussed. ฉ 2018 De Gruyter Mouton. All rights reserved.
Keywords
Keyness, Keyword, Keyword identification, Log-likelihood
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