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Presentation on theme: "THE PERCENTAGE OF WORDS KNOWN IN A TEXT AND READING COMPREHENSION"— Presentation transcript:

Norbert Schmitt University of Nottingham Xiangying Jiang West Virginia University William Grabe Northern Arizona University

2 Reading Performance and Vocabulary Knowledge are Strongly Related
(Laufer, 1992) (Qian, 1999) (Qian, 2002)

3 The Ability to Read Requires A Large Vocabulary
How Much? Early Research 3,000 word families (Laufer, 1992) 5,000 individual words (Hirsh and Nation, 1992) 5,000 words Laufer (1989)

4 The Ability to Read Requires A Large Vocabulary
How Much? Recent Research 8,000-9,000 word families (Hu and Nation 2000; Nation, 2006) 1st 1,000 word families average about 6 members (types per family) 9th 1,000 frequency level average 3 members SO 8,000 word families = 34,660 individual word forms

5 Why Different Estimates? 3,000 vs 9,000 Word Families
Different criteria of ‘adequate’ comprehension (Laufer – 55%) Short texts Small participant numbers (66) Old frequency counts (Dutch) Determination of unknown words

6 Vocabulary Coverage Laufer (1989) found 95% coverage was point which best distinguished ‘comprehenders’ vs. ‘noncomprehenders’ 95%  3,000 word families Hu and Nation (2000) tested comprehension at various coverages 80% = No learners had adequate comprehension 90% = Only a few 95% = % At 95% coverage, less than half of the students were successful, so required coverage is higher: 98-99% 98-99%  8,000-9,000 word families

7 Vocabulary Coverage So the vocabulary coverage requirement is critical: 3,000 vs 9,000 word families This study will directly explore the relationship between vocabulary coverage and reading comprehension

8 Vocabulary Coverage / Reading Comprehension

9 Vocabulary Coverage / Reading Comprehension

10 Vocabulary Coverage / Reading Comprehension

11 Features of Our Study Longer texts (582 and 757 words)
Extensive vocabulary test Extensive reading comprehension tests Controlled for background knowledge of texts 664 participants from different L1s

12 Selection of Reading Passages
CLIMATE MICE Length 757 words 582 words Content Climate change and global warming A study on the relationship between exercise and mental acuity Prior knowledge With much prior knowledge With little prior knowledge Difficulty Flesch-Kincaid Grade Level: 9.8 Flesch-Kincaid Grade Level: 9.7

13 Development of the Vocabulary Test
a checklist format (check the words they know) 120 target words sampled from the texts and 30 nonwords deleted anybody with over 3 nonwords checked (≥2 nonwords same result) high sampling rate for a good estimate of how much vocabulary each learner knew in each text

14 Development of the Reading Comprehension Tests
A two-part reading test for each passage 14 multiple-choice items 16 graphic organizer completion items graphic organizers were created to reflect the major discourse structures of the text fill in partially-completed graphic organizers

15 Participants L1 # Levels Turkish 292 IEP 135 Chinese 180 Freshman 270
Arabic 101 Sophomore 143 Spanish 33 Junior 43 Hebrew 26 Senior 50 Other lgs 32 Graduate 23 Total 664

16 Procedure 100 minutes for the entire test battery
Biodata survey (5 mins.) Vocabulary checklist (15 mins.) Reading the Climate passage and answer comprehension items (40 mins.) Reading the Mice passage and answer comprehension items (40 mins.)

17 Initial Screening Eliminated participants who checked more than 3 nonwords Eliminated participants who attempted less than 5 items in the graphic organizer task for either passage

18 Scoring Vocabulary percentage
automatically calculated by entering checklist selections into an EXCEL spreadsheet Multiple-choice reading comprehension test 1 point for each correct answer, 0 for incorrect ones Graphic organizer reading comprehension test 1 point for each acceptable answer and 0 for unacceptable ones Interrater reliability .99

19 Reliability Estimates of the Reading Test
.82 for the entire reading test .79 for the Climate reading test .65 for the Mice reading test .59 for the multiple-choice items .81 for the graphic organizer items Note: based on KR-21, possible underestimation

20 Vocabulary Coverage vs Reading Comprehension

21 The Influence of Background Knowledge

22 Graphic Organizer vs Multiple-Choice Tests

23 Conclusions The vocabulary coverage / comprehension relationship is essentially linear between 90% - 100% coverage So coverage requirements depends on comprehension goals 98% coverage is probably necessary, as 70% comprehension is desirable But even 90% coverage leads to 50% comprehension 100% coverage only lead to 75% comprehension, so successful reading requires more than vocabulary, but high vocabulary levels are clearly a key requirement Higher background knowledge lead to about 10 percentage-points better comprehension There is a large amount of variation among learners


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