Editing Shuffling (section)

===Sufficiency===
The number of shuffles that are sufficient for a "good" level of randomness depends on the type of shuffle and the measure of "good enough randomness", which in turn depends on the game in question. For most games, four to seven riffle shuffles are sufficient: for [[suit (cards)|unsuited]] games such as [[blackjack]], four riffle shuffles are sufficient, while for suited games, seven riffle shuffles are necessary. There are some games, however, for which even seven riffle shuffles are insufficient.<ref name="vzs2004">{{Harv|Van Zuylen|Schalekamp|2004}}</ref>

In practice the number of shuffles required depends both on the quality of the shuffle and how significant non-randomness is, particularly how good the people playing are at noticing and using non-randomness. Two to four shuffles is good enough for casual play. But in club play, good [[contract bridge|bridge]] players take advantage of non-randomness after four shuffles,<ref name="kolata" /> and top blackjack players supposedly track aces through the deck; this is known as "ace tracking", or more generally, as "[[shuffle track]]ing".{{Citation needed|date=February 2007}}