Hardly any of you reading this does not know what insurance in blackjack is, but we will still refresh your memory of this moment the rules. Insurance is offered to a player if a dealer opens an ace. If you think that it is a hand of black-jack, you can protect yourself from a loss, taking a half as insurance. If a dealer has blackjack, insurance is paid in the ratio of two to one.
According to the basic strategy, insurance is disadvantageous for the player, so using it is not recommended. However not everything is so simple, if you count cards. In such a case you should not always respond to failure with insurance.
We will not go into lengthy mathematical calculations. Let's just say that if you use counting system of High/Low (also known as "Plus/Minus"), it is possible to agree on the insurance if the real (we emphasize REAL) score is above 3.3. According to the "halves", this value should not be less than 3.7.
However if you are not using the system of card counting, you can consider just dozens that remain in the shoe. If the probability of the dealer's score is above third, take it. For example, you can assign released dozens "-2", and other cards "1". If the result of the counting exceeds "24", it means that insurance becomes effective. However it is better to use a common card counting with one of the systems than bother asking for profitability of insurance.
Another kind of insuranceis offering "equal money." If you have a blackjack and the dealer opened the ace, it gives you the opportunity to immediately get a prize in the amount of 1:1. Without counting cards,it is not necessary to accept the proposal, since it means the average gain in the 26/27 ratio. As you can see, by refusing, you save 1/27 of beys.
All calculations given above are for conventional insurance and its appropriateness in counting cards is valid for "equal money." However whether or not to complicate the game because of such small advantages, you decide. In any case, if you master the card counting, it is best to initially refuse from insurance.
Finally, we note that in Some casinos the insurance from dealer's ten should be always ignored, because usually ace can comes out only once in thirteen cards.