Selection Effects

4 pages on this site touch on this topic.

• Multiple Comparisons — Run many independent tests and watch how quickly the chance of at least one false positive climbs — even though no single test got any less reliable.
• Multiple opportunities and selection effects — Why running many chances at a pattern makes finding one almost guaranteed, even when every individual chance was unlikely on its own.
• Selection effects: what you see isn't random — When data has already been filtered by its own outcome, conclusions drawn from it can be exactly backwards, as WWII aircraft-armor analysis shows.
• The Jim twins: separated at birth — Twins reunited at 39 shared striking habits — a story that launched a landmark genetics study, and a real debate about how it was reported.