手法を比較

	ブロック化A/Bテスト	多群実験
分野	実験計画法	実験計画法
系統	Process / pipeline	Process / pipeline
提唱年	1926 (blocking principle); 2000s–2010s (online A/B testing application)	1990s–2000s (clinical formalization); multi-arm concept implicit in ANOVA-era factorial designs
提唱者	R. A. Fisher (blocking principle); adapted to online A/B testing by industry practitioners	Developed within clinical trials methodology; formalized by Parmar, Royston and colleagues (UK MRC CTU, early 2000s)
種類	Randomized controlled experiment with variance reduction	Experimental design
原典	Fisher, R. A. (1926). The arrangement of field experiments. Journal of the Ministry of Agriculture of Great Britain, 33, 503–513.	Royston, P., Parmar, M. K. B., & Qian, W. (2003). Novel designs for multi-arm clinical trials with survival outcomes with an application in ovarian cancer. Statistics in Medicine, 22(14), 2239–2256.
別名	block-randomized A/B test, stratified A/B test, blocked split test, block-design A/B experiment	multi-arm trial, multiple-arm experiment, multi-group experiment, many-arm design
関連	4	5
概要	A blocked A/B test is an experimental design that partitions units (users, subjects, or clusters) into homogeneous blocks before randomly assigning them to treatment A or treatment B within each block. Blocking reduces within-experiment noise by ensuring that known sources of variation — such as device type, geography, or user tenure — are balanced across conditions, yielding more precise estimates of the treatment effect than a simple unblocked A/B test.	A multi-arm experiment simultaneously compares three or more treatment or intervention conditions — each called an arm — against a shared control or against one another. By testing multiple alternatives in a single study, it yields more information per participant than running separate two-group experiments sequentially, while controlling the overall Type I error rate through pre-specified comparison strategies.