Insurance bet

Insurance is a bad bet for the non-counting player who has no knowledge of the hole card because it has a house edge of 2% to 15%, depending on number of decks used and visible 10-cards. Essentially, taking insurance amounts to betting that the dealer's hole card is a ten or face card. Since in an infinite deck, 4/13 of the cards are tens or face cards, an unbiased insurance wager would actually pay 9:4, or 2.25:1; since the bet only pays 2:1, the house has a strong advantage. However, if the player has been counting cards, he may know that more than a third of the deck is ten-value cards, in which case insurance becomes a good bet