Editing Shuffling (section)

===Riffle===
[[File:Riffle Shuffle.jpg|thumb|right|Cards lifted after a riffle shuffle, forming what is called a bridge which puts the cards back into place]]
[[File:Riffle shuffle 1.jpg|thumb|right|After a riffle shuffle, the cards cascade]]
A common shuffling technique is called the ''riffle,'' or ''dovetail'' shuffle or ''leafing the cards'', in which half of the deck is held in each hand with the thumbs inward, then cards are released by the thumbs so that they fall to the table interleaved. Many also lift the cards up after a riffle, forming what is called a bridge which puts the cards back into place; it can also be done by placing the halves flat on the table with their rear corners touching, then lifting the back edges with the thumbs while pushing the halves together. While this method is more difficult, it is often used in [[casino]]s because it minimizes the risk of exposing cards during the shuffle. There are two types of perfect riffle shuffles: if the top card moves to be second from the top then it is an [[in shuffle]], otherwise it is known as an [[out shuffle]] (which preserves both the top and bottom cards).

The [[Gilbert–Shannon–Reeds model]] provides a mathematical model of the random outcomes of riffling that has been shown experimentally to be a good fit to human shuffling<ref>{{citation
 | last = Diaconis | first = Persi | author-link = Persi Diaconis
 | isbn = 0-940600-14-5
 | location = Hayward, CA
 | mr = 964069
 | publisher = Institute of Mathematical Statistics
 | series = Institute of Mathematical Statistics Lecture Notes—Monograph Series, 11
 | title = Group representations in probability and statistics
 | year = 1988}}.</ref> and that forms the basis for a recommendation that card decks be riffled seven times in order to randomize them thoroughly.<ref>{{cite news |title=In Shuffling Cards, 7 Is Winning Number|first=Gina|last=Kolata|author-link=Gina Kolata |work=[[The New York Times]]|url=https://www.nytimes.com/1990/01/09/science/in-shuffling-cards-7-is-winning-number.html|date=January 9, 1990}}.</ref> Later, mathematicians [[Lloyd M. Trefethen]] and [[Lloyd N. Trefethen]] authored a paper using a tweaked version of the Gilbert–Shannon–Reeds model showing that the minimum number of riffles for total randomization could also be six, if the method of defining randomness is changed.<ref>{{cite news |title=Shuffling, what's the Deal? |url=https://www.nature.com/news/2000/001005/full/news001005-8.html}}</ref>{{sfn|Trefethen|Trefethen|2000}}