THE INFLUENCES OF ORAL PRESENTATIONS ON VOCABULARY DEVELOPMENT IN TERMS OF LEXICAL DIVERSITY AND LEXICAL DENSITY: A QUASI-EXPERIMENTAL STUDY IN A GRADE 8 CLASS AT DOAN THI DIEM JUNIOR SECONDARY SCHOOL

Abstract

The present study was designed to determine the extent to which EFL students can enhance their level of lexical diversity and density through regular practice of oral presentations in English lessons. A quasi-experimental design was used. The study population consisted of 16 students in a grade 8 class at Doan Thi Diem Secondary school. During the experimental period of 10 weeks in semester two of the school year 2014-2015, the students had to give six oral presentations in groups. Firstly, lexical diversity of the first presentation (pre-test) and of the last one (post-test) was measured, using D or Voc-D measure. Lexical density of the two tests was also measured by calculating the proportion of content words over the total number of words. Then the difference in lexical density and diversity between the pre-test and was examined using a t-test. The results have shown that regular practice of oral presentations in English have significantly improved the students’ vocabulary lexical diversity and lexical density.

Key words: Oral Presentation, vocabulary development, lexical density, and lexical diversity.