Cost of insurance mistake

**NotEnoughHeat** · 01-21-2016, 05:30 AM

I'm sure that I might be able to find this somewhere in the resources available to me but I'm having a hard time.

Last session I accidentally missed a large insurance bet and I've been kicking myself all day for it.

What's the cost of not insuring two hands of 150 at a RC of +9 at about 1.75 decks remaining out of 6 (I could have just given the TC but I want to leave the extra info in case some body wants to work in depth)

Thanks

RS · 01-21-2016, 07:26 AM

HiLo?

My thought process is with a TC of +5, you expect to have 1 extra TJQKA of each per deck, so 20/52 cards are expected to be face cards.

((20/52)*300 - (32/52)*150) = $23.07.

Or perhaps it should be done the other way [by removing 5 little cards]. I don't know for sure, but I'd guess I'm fairly close with the $23 figure (+/- $2 perhaps?), unless there's some major flaw in my logic.

I'm sure others will chime in and have it nailed down to the T, including charts or graphs.

**NotEnoughHeat** · 01-21-2016, 07:31 AM

That seems like a reasonable calculation. I think various methods of answering this question are valid but just consider different information or make different assumptions.

At the time I had it in my head that it was 2 decks and that I was 1 RC away from the index in the wrong direction.

**Freightman** · 01-21-2016, 08:00 AM

Originally Posted by NotEnoughHeat

That seems like a reasonable calculation. I think various methods of answering this question are valid but just consider different information or make different assumptions.

At the time I had it in my head that it was 2 decks and that I was 1 RC away from the index in the wrong direction.

Taking into account your calculate error, TC would still have been 4.0, well exceeding your break even hi Lo TC 3.0.. Brain farts happen.

**DSchles** · 01-21-2016, 08:14 AM

Insurance is just about the only linear play in the game, meaning that your edge, per true count, increases at the same rate as the count goes up. If I remember correctly, the per-TC-edge for insurance is about 2.3%. As 9/1.75 = 5.14, your TC exceeded the +3 breakeven value by 2.14, and 2.14 x 2.3% = 4.92%. 4.92% of your $300 bet is $14.77, but you insure for only half of that amount, so I'd say the error cost you $7.38 in expectation.

Don

RS · 01-21-2016, 08:23 AM

My original guess was closer to Dons' answer. I should'a ignored the trying-to-do-the-math. Argh!

Don, how would you determine the EV he gave up without already knowing 1 TC change = 2.3% EV on insurance? Rather, how would you logically figure out the EV (i.e.: "there are 5 fewer little cards than big card per deck, therefore...")?

**DSchles** · 01-21-2016, 08:39 AM

"Don, how would you determine the EV he gave up without already knowing 1 TC change = 2.3% EV on insurance? Rather, how would you logically figure out the EV (i.e.: "there are 5 fewer little cards than big card per deck, therefore...")?"

While I'm not a big fan of the "representative decks" concept for assuming what the proportion of large to small cards is at any given true count, that would be the way to do it. See Griffin, p. 24, "Insurance is linear" discussion.

Don

**Tarzan** · 01-25-2016, 09:16 PM

At TC+5 you take insurance but if the high count is due to a bunch of surplus Aces the insurance count is going to be lower than the TC. Surplus middle cards lower the insurance count. I use an insurance count derived from my running count that takes this into account with the only cards not factored in burn cards and the dealer's hole card for perfect insurance correlation. Having a second player doing a separate insurance count would work also. I'm sort of questioning why you hesitated taking insurance with that count... that would have been worth two hotdogs on the boardwalk for sure... with sauerkraut!

**NotEnoughHeat** · 01-27-2016, 12:05 PM

Originally Posted by Tarzan

questioning why you hesitated taking insurance with that count... that would have been worth two hotdogs on the boardwalk for sure... with sauerkraut!

Like I said above, just had a brain fart I thought I was 1 below the index instead of above. Also, at the time I thought it might have been closer to 2 decks while in hindsight it might have been lower. Probably my 3rd session after a 2 or 3 month break so some my index plays were slower than usual.