A corpus-based study of modal verbs in English textbooks for junior high schools used in Japan

This paper constructed a textbooks corpus with English textbooks for junior high schools used in Japan (approximately 60,000 words) to see whether or not the frequencies of modal auxiliary verbs in each grade and in each modal auxiliary verb were statistically different.The Friedman test was applied to answer these questions.As a result, there were statistically significant differences in general among the grades and among modal auxiliary verbs while the post hoc comparisons did not show significance.This could be because of Bonferroni's correction.Even though the result of the comparison was not like our expectation, it could be inferred that there were differences between Grade 2 and Grade 1 and 3 as well as there were differences between "can", "will", and the others.