Deal or No Deal (also known by its initialism DOND) is the name of several closely related television game shows, the first of which (launching the format) was the Dutch Miljoenenjacht (Hunt/Chase for Millions).
The centerpiece of this format is the final round (a.k.a. the "case game" or "main game") which is played with up to 26 cases (or, in some versions, boxes), each containing randomly assigned sums of money. After the player for the case game is determined, this contender claims one case or a box at the start of the game, without its contents being revealed. The contestant then chooses the other cases or boxes, one at a time, to be immediately opened and removed from play. Throughout the game, the player is offered an amount of money or prizes to sell back their case and end the game, being asked the titular question, "Deal or No Deal?" If the contestant rejects every deal and eliminates all the other cases, the player keeps the money that was in their case. While almost all contestants win money, a winning outcome is dependent on whether the player should have taken one of the deals or should have held onto the original case or box until the very end.
Gameplay
The gameplay of the show differs from country to country. In some countries, there is a preliminary contest in which the studio audience is whittled down to one final contender by several trivia question rounds, this final contender then proceeds to the main game. This was the format used by the Dutch show Miljoenenjacht (Hunt/Chase for Millions) which initiated the Deal or No Deal game (the initial version of the Dutch show was based on a German format called Die Chance deines Lebens (The Chance of your Lifetime), which was based on trivia questions and did not have the briefcase element at all). There are also some versions with the number of players equal to the number of cases, each player receives one case. Via a short trivia round or a random selection, one player is selected to be the contestant for the main game with their case. In other countries, there is only one preselected contestant who will play the main game without any preliminary contest.
The main game revolves around the opening of a set of numbered briefcases, each of which contains a different prize (cash or otherwise). The contents (i.e., the values) of all of the cases are known at the start of the game, but the specific location of any prize is unknown. The contestant claims (or is assigned) a case to begin the game. The case's value is not revealed until the conclusion of the game.
The contestant then begins choosing cases that are to be removed from play. The amount inside each chosen case is immediately revealed; by process of elimination, the amount revealed cannot be inside the case the contestant initially claimed (or was assigned). Throughout the game, after a predecided number of cases have been opened, the "Banker" offers the contestant an amount of money and/or prizes to quit the game; the offer is based roughly on the amounts remaining in play and the contestant's demeanor, so the bank tries to 'buy' the contestant's case for a lower price than what's inside the case. The player then answers the titular question, choosing:
"Deal", accepting the offer presented and ending the game, or "No Deal", rejecting the offer and continuing the game.
This process of removing cases and receiving offers continues, until either the player accepts an offer to 'deal', or all offers have been rejected and the values of all unchosen cases are revealed. Should a player end the game by taking a deal (except if the deal was made in the final round), a pseudo-game is continued from that point to see how much the player could have won by remaining in the game. Depending on subsequent choices and offers, it is determined whether or not the contestant made a "good deal", i.e. won more than if the game were allowed to continue.
Since the range of possible values is known at the start of each game, how much the banker offers at any given point changes based on what values have been eliminated (i.e. the offer increases if lower values are eliminated and decreases if upper values are eliminated). To promote suspense and lengthen games, the banker's offer is usually less than the expected value dictated by probability theory, particularly early in the game. Generally, the offers early in the game are very low relative to the values still in play, but near the end of the game approach (or even exceed) the average of the remaining values.
Only a few people have ever won the top prize on any version of the show (see table below). For a contestant to win the top prize the player would have to select the case containing the top prize and reject every offer the banker makes during the game. The chances of a player selecting the top prize are 4–5% depending on how many amounts are in the game.
International versions
Top prize winners
All amounts below the prizes are their equivalents in United States dollars at the time of their win.