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	グラッドマン尺度	フロア・シーリング効果
分野	心理測定学	心理測定学
系統	Process / pipeline	Process / pipeline
提唱年	1944	2000
提唱者	Louis Guttman	Classical psychometrics
種類	Cumulative unidimensional scaling methodology	Measurement validity assessment
原典	Guttman, L. (1944). A basis for scaling qualitative data. American Sociological Review, 9(2), 139-150.	McHorney, C. A. (2000). Ten recommendations for measuring health status. Health-Related Quality of Life Outcomes, 2(1), 1-5.
別名	Cumulative scale, Scalogram analysis, Guttman scaling, Unidimensional cumulative scale	Floor effect, Ceiling effect, Psychometric floor effect, Measurement floor
関連	4	4
概要	Guttman scaling is a methodology for constructing unidimensional scales with a cumulative property, developed by Louis Guttman in 1944. The method assumes that items form a perfect or near-perfect hierarchy: if a respondent endorses a harder item, they must endorse all easier items below it. This creates a reproducible scale structure useful for measuring constructs with ordinal properties such as difficulty, intensity, or severity.	Floor and ceiling effects are psychometric phenomena in which a disproportionately large proportion of respondents achieve the lowest (floor) or highest (ceiling) possible score on a measurement scale. These effects compromise scale reliability and responsiveness, limiting the instrument's ability to distinguish among respondents and detect meaningful change over time. Systematic assessment of floor and ceiling effects is essential for evaluating the psychometric adequacy of health-related quality-of-life scales, functional status measures, and other patient-reported outcomes.