手法を比較

	クロスオーバー自然実験	クロスオーバーランダム化比較試験（Crossover Randomized Controlled Trial）
分野	実験計画法	実験計画法
系統	Process / pipeline	Process / pipeline
提唱年	Crossover designs: mid-20th century; applied to natural experiments: 1990s–2000s	1960s (Grizzle 1965 for statistical foundations); widely used in clinical research since the 1970s
提唱者	Drawn from crossover trial methods (Jones & Kenward) and natural experiment tradition (Mill, 1843; Dunning, 2012)	Early formalized by statisticians including Bradford Hill and colleagues in clinical trials; theoretical framework developed by Grizzle (1965) and later Senn (2002)
種類	Quasi-experimental design	Experimental within-subject design
原典	Dunning, T. (2012). Natural Experiments in the Social Sciences: A Design-Based Approach. Cambridge University Press. ISBN: 978-1107698000	Senn, S. (2002). Cross-over Trials in Clinical Research (2nd ed.). Wiley. ISBN: 978-0471496533
別名	within-unit natural experiment, reversal natural experiment, crossover quasi-experiment	crossover RCT, crossover trial, within-subject RCT, AB/BA crossover design
関連	5	5
概要	A crossover natural experiment exploits an externally imposed condition — a policy change, law, or environmental event — that exposes the same units (individuals, regions, firms) to both treatment and control states at different times. By observing each unit in multiple conditions, researchers use within-unit variation to estimate causal effects without researcher-controlled randomization, combining the internal validity advantage of crossover designs with the real-world relevance of natural experiments.	A crossover randomized controlled trial (crossover RCT) is an experimental design in which each participant receives all study interventions in a randomized sequence, separated by a washout period. Because every participant serves as their own control, within-subject variability is eliminated from the treatment comparison, yielding greater statistical power per participant than a parallel-group RCT of equal size.