The 1854 cholera outbreak is the example of a natural experiment discussed often by David A. Freedman, e.g. in Statistical Models: Theory and Practice (Cambridge University Press) [1] （页面存档备份，存于互联网档案馆）, chapter 1.3 (pages 6-9).
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The 1854 cholera outbreak is the example of a natural experiment discussed often by David A. Freedman, e.g. in Statistical Models: Theory and Practice (Cambridge University Press) [1] （页面存档备份，存于互联网档案馆）, chapter 1.3 (pages 6-9).
