Coin flipping
Coin flipping, coin tossing, or heads or tails involves using the thumb to launch a coin in the air and then checking which side is showing once it has landed, in order to randomly choose between two alternatives. It is a form of sortition which inherently has two possible outcomes.
History
Coin flipping was known to the Romans as navia aut caput, as some coins had a ship on one side and the head of the emperor on the other.In England, this was referred to as cross and pile.
Process
During a coin toss, the coin is thrown into the air such that it rotates edge-over-edge an unpredictable number of times. Either beforehand or when the coin is in the air, an interested party declares "heads" or "tails", indicating which side of the coin that party is choosing. The other party is assigned the opposite side. Depending on custom, the coin may be caught; caught and inverted; or allowed to land on the ground. When the coin comes to rest, the toss is complete and the party who called correctly or was assigned the upper side is declared the winner.It is possible for a coin to land on its side, usually by landing up against an object or by getting stuck in the ground, and sometimes even on a flat surface. A computational model suggests that the chance of a coin landing on its edge and staying there is about 1 in 6,000 for an American nickel.
The coin may be any type as long as it has two distinct sides. Larger coins tend to be more popular than smaller ones. Some high-profile coin tosses, such as those in the Cricket World Cup and the Super Bowl, use custom-made ceremonial medallions.
Three-way
Three-way coin flips are also possible, by a different process—this can be done either to choose one or two out of three. To choose two out of three, three coins are flipped, and if two coins come up the same and one different, the different one loses, leaving two players. To choose one out of three, the previous is either reversed or a regular two-way coin flip between the two remaining players can decide. The three-way flip is 75% likely to work each time it is tried, and does not require that "heads" or "tails" be called.A well-known example of such a three-way coin flip is dramatized in Friday Night Lights, wherein three Texas high school football teams use a three-way coin flip. A legacy of that particular 1988 coin flip was to reduce the use of coin flips to break ties in Texas sports, instead using point systems to reduce the frequency of ties.
Larger numbers
"Heads and Tails" or "Heads or Tails" is an informal game of chance using repeated coin tosses, suitable for a roomful of seated people, typically a social or children's event. Initially all players stand. Before each coin toss, all still standing put their hands on either their head to indicate "heads" or their hips or buttocks to indicate "tails"; once the toss result is announced, those who guessed incorrectly sit down. The process repeats until the last player standing wins; often the last few players remaining are called to the announcer's table for the climax. A variant with faster elimination is played with two coins and players placing each hand separately.Use in dispute resolution
Coin tossing is a simple and unbiased way of settling a dispute or deciding between two or more arbitrary options. In a game theoretic analysis it provides even odds to both sides involved, requiring little effort and preventing the dispute from escalating into a struggle. It is used widely in sports and other games to decide arbitrary factors such as which side of the field a team will play from, or which side will attack or defend initially; these decisions may tend to favor one side, or may be neutral. Factors such as wind direction, the position of the sun, and other conditions may affect the decision. In team sports it is often the captain who makes the call, while the umpire or referee usually oversees such proceedings. A competitive method may be used instead of a toss in some situations, for example in basketball the jump ball is employed, while the face-off plays a similar role in ice hockey.Coin flipping is used to decide which end of the field the teams will play to and/or which team gets first use of the ball, or similar questions in football matches, American football games, Australian rules football, volleyball, and other sports requiring such decisions. In the U.S. a specially minted coin is flipped in National Football League games; the coin is then sent to the Pro Football Hall of Fame, and other coins of the special series minted at the same time are sold to collectors. The original XFL, a short-lived American football league, attempted to avoid coin tosses by implementing a face-off style "opening scramble," in which one player from each team tried to recover a loose football; the team whose player recovered the ball got first choice. Because of the high rate of injury in these events, it has not achieved mainstream popularity in any football league, and coin tossing remains the method of choice in American football.
In an association football match, the team winning the coin toss chooses which goal to attack in the first half; the opposing team kicks off for the first half. For the second half, the teams switch ends, and the team that won the coin toss kicks off. Coin tosses are also used to decide which team has the pick of going first or second in a penalty shoot-out. Before the early-1970s introduction of the penalty shootout, coin tosses were occasionally needed to decide the outcome of drawn matches where a replay was not possible. The most famous instance of this was the semifinal game of the 1968 European Championship between Italy and the Soviet Union, which finished 0–0 after extra time. Italy won, and went on to become European champions.
File:BradmanAllenToss.jpg|right|thumb|Tossing a coin is common in many sports, such as cricket, where it is used to decide which team gets the choice of bowling or batting first. Shown are Don Bradman and Gubby Allen tossing for innings.
In cricket the toss is often significant, as the decision whether to bat or bowl first can influence the outcome of the game. Factors such as pitch conditions, weather and the time of day are considered by the team captain who wins the toss.
Similarly, in tennis a coin toss is used in professional matches to determine which player serves first. The player who wins the toss decides whether to serve first or return, while the loser of the toss decides which end of the court each player plays on first.
In duels a coin toss was sometimes used to determine which combatant had the sun at his back.
In some other sports, the result of the toss is less crucial and merely a way to fairly choose between two more or less equal options.
The National Football League also has a coin toss for tie-breaking among teams for playoff berths and seeding, but the rules make the need for coin toss, which is random rather than competitive, very unlikely. A similar procedure breaks ties for the purposes of seeding in the NFL draft; these coin tosses are more common, since the tie-breaking procedure for the draft is much less elaborate than the one used for playoff seeding.
Major League Baseball once conducted a series of coin flips as a contingency on the last month of its regular season to determine home teams for any potential one-game playoff games that might need to be added to the regular season. Most of these cases did not occur. From the 2009 season, the method to determine home-field advantage was changed.
Fédération Internationale d'Escrime rules use a coin toss to determine the winner of some fencing matches that remain tied at the end of a "sudden death" extra minute of competition. Although in most international matches this is now done electronically by the scoring apparatus.
In the United States Asa Lovejoy and Francis W. Pettygrove, who each owned the claim to the land that would later become Portland, Oregon, wanted to name the new town after their respective hometowns of Boston, Massachusetts and Portland, Maine; Pettygrove won with the flip of a coin which has been preserved as the Portland Penny.
Scientists sometimes use coin flipping to determine the order in which they appear on the list of authors of scholarly papers.
In addition to its practical applications in sports, coin tossing is symbolic of the democratic principle of equal opportunity. When two parties face an impasse, the act of flipping a coin signifies a commitment to impartiality and a willingness to accept the outcome, no matter how arbitrary it may seem. This shared acceptance of chance as the ultimate arbiter can foster cooperation and conflict resolution in various aspects of life beyond sports, including business negotiations and interpersonal conflicts.
Game
The party who calls the side that is facing up when the coin lands wins.The precedent necessity for win in the dual state flip has motivated methods for cheating so as to improve or ensure a win in an apparently random event.