got bad beat up, why?? pro help

[bjplayer123]

I went casino this weekend, and played 6D s17 surrender game.

I played 3 tables, eat table about 4 to 6 hours, my bet rang was from $25 to $45. I followed basic strategy card 100% off time, because boook says Casino edge is only 0.5 That means every hundred $ i bet i should only lose 50 cents mathmatically, but why i lost $2500 in 15 hours, i always like to play full table, so it takes about 20 minutes to play 10 to 15 hands. I calculate i shouldnt lose more than two hundred if i play 15 hours. Why $2500

Am i just been bad luck or i calculated wrong

pro help

 

[gronbog]

Your expected value (EV) may be approximately 0.5% or about 50 cents for every $100 bet, but it is very unlikely to be anywhere close to that over the short term (and yes, 12 to 18 hours is very much the short term!). In reality, your results will be in a range which depends on the standard deviation of the game.

Most blackjack games have a standard deviation close to 1.1. As you play, the standard deviation of your expected result grows as the square root of the number of rounds played. So the standard deviation of your sessions is (averageBet x standardDeviation x SQRT (rounds played)). This all assumes that you played one spot.

Taking some numbers from your post, you said you played about 15 hours at perhaps a max of 45 rounds per hour. 15 hours at 45 rounds per hour is 675 rounds. Let's put your average bet at $35 (mid way between $25 and $45). So the standard deviation for your total play is estimated at $35 x 1.1 * SQRT(675) or $35 x 1.1 * 25.98 = $1,000.23. Your expected loss was approximately $35 x 675 x 0.005 or $118.13.

Now what you need to know about your total standard deviation is that you have approximately a 68% chance of ending up between +1 and -1 standard deviations, approximately a 95% chance of ending up between +2 and -2 standard deviations and approximately a 98% chance of ending up between +3 and -3 standard deviations. Your actual loss was $2500 which is -2381.87 or -2.38 standard deviations from your expected loss. While rare, this is certainly not a wildly unexpected result.

 

[Meistro]

Well you probably aren't playing perfect basic strategy, so that is also going to be a factor. If your disadvantage is more like 1.5%, then with an average bet of $35 and 50 rounds per hour that is action of 1750 an hour. You claimed to play for 15 hours so that is 26250 in action so your expected loss is now in the $400 range. So basically you are playing bad and running bad.