Uber useful!!!<\/p>\n
Estimating the chances of something that hasn\u2019t happened yet
\nby John on March 30, 2010
\nSuppose you\u2019re proofreading a book. If you\u2019ve read 20 pages and found 7 typos, you might reasonably estimate that the chances of a page having a typo are 7\/20. But what if you\u2019ve read 20 pages and found no typos. Are you willing to conclude that the chances of a page having a typo are 0\/20, i.e. the book has absolutely no typos?
\nTo take another example, suppose you are testing children for perfect pitch. You\u2019ve tested 100 children so far and haven\u2019t found any with perfect pitch. Do you conclude that children don\u2019t have perfect pitch? You know that some do because you\u2019ve heard of instances before. But your data suggest perfect pitch in children is at least rare. But how rare?
\nThe rule of three gives a quick and dirty way to estimate these kinds of probabilities. It says that if you\u2019ve tested N cases and haven\u2019t found what you\u2019re looking for, a reasonable estimate is that the probability is less than 3\/N. So in our proofreading example, if you haven\u2019t found any typos in 20 pages, you could estimate that the probability of a page having a typo is less than 15%. In the perfect pitch example, you could conclude that fewer than 3% of children have perfect pitch.
\nvia Estimating the chances of something that hasn\u2019t happened yet \u2014 The Endeavour<\/a>.<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"Uber useful!!! Estimating the chances of something that hasn\u2019t happened yet by John on March 30, 2010 Suppose you\u2019re proofreading a book. If you\u2019ve read 20 pages and found 7 typos, you might reasonably estimate that the chances of a page having a typo are 7\/20. But what if you\u2019ve read 20 pages and found … <\/p>\n