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THE PERCENTAGE OF WORDS KNOWN IN A TEXT AND READING COMPREHENSION Norbert Schmitt University of Nottingham Xiangying Jiang West Virginia University William.

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Presentation on theme: "THE PERCENTAGE OF WORDS KNOWN IN A TEXT AND READING COMPREHENSION Norbert Schmitt University of Nottingham Xiangying Jiang West Virginia University William."— Presentation transcript:

1 THE PERCENTAGE OF WORDS KNOWN IN A TEXT AND READING COMPREHENSION Norbert Schmitt University of Nottingham Xiangying Jiang West Virginia University William Grabe Northern Arizona University

2 R eading 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% = 35-41% 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

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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 CLIMATEMICE Length757 words582 words ContentClimate change and global warming A study on the relationship between exercise and mental acuity Prior knowledgeWith much prior knowledge With little prior knowledge DifficultyFlesch-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# Turkish292IEP135 Chinese180Freshman270 Arabic101Sophomore143 Spanish33Junior43 Hebrew26Senior50 Other lgs32Graduate23 Total664

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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