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Bloom's 2 sigma problem refers to an educational phenomenon observed by educational psychologist Benjamin Bloom and initially reported in 1984 in the journal "Educational Researcher". Bloom found that the average student tutored one-to-one using mastery learning techniques performed two standard deviations better than students who learn via conventional instructional methods〔Bloom 1984, pp. 4-16〕—that is, "the average tutored student was above 98% of the students in the control class".〔Bloom 1984, p. 4〕 Additionally, the variation of the students' achievement changed: "about 90% of the tutored students ... attained the level of summative achievement reached by only the highest 20%" of the control class.〔Bloom 1984, p.4〕 Bloom's graduate students J. Anania and A. J. Burke conducted studies of this effect at different grade levels and in different schools, observing students with "great differences in cognitive achievement, attitudes, and academic self-concept".〔Bloom 1984, p. 15〕 ==Objects of change process== Though Bloom concluded that one-to-one tutoring is "too costly for most societies to bear on a large scale", Bloom conjectured that a combination of two or three altered variables may result in a similar performance improvement. Bloom thus challenged researchers and teachers to "find methods of group instruction as effective as one-to-one tutoring".〔Bloom 1984, p. 15〕 Bloom classified alterable variables that may have, in combination, a 2 sigma effect as the following "objects of change process": # Learner # Instructional material # Home environment or peer group # Teacher Bloom and his graduate students considered and tested various combinations of these variables, focusing only on those variables that individually had a 0.5 or higher effect size. These included: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bloom's 2 Sigma Problem」の詳細全文を読む スポンサード リンク
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