- Thread starter felix
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I don't know why they are different. 6D vs. 4D is pretty close. I used Wong's PBJA software which computes the indices using combinatorial analysis and not using computer simulation of millions of hands. I am sure either set will work just fine. I have confidence that Wong's software gives exactly the right index as predicted by combinatorial analysis. Indeed, the indices his software predicts for the Halves system directly contradict in many cases those published in his own book, Professional Blackjack!

The thing to remember is that the true value of an index is not worth very much in practical terms. For example, the most commonly used index is 16 vs. T, which is variously quoted as 0 or +1. If you play that index as +2 for your entire life the amount of EV you give up wouldn't buy a cup of coffee.

Think about it, how often do you make the decision 16-T when the count is actually between 0 and 1? So first of all, the even is extremely rare. Then, the index is the break even point between the two plays, hence right around the index you could pick one play or the other and they would be roughly even in their EV. Thus, for practical purposes, all indices are approximate, and if the value given is within 1 of the "correct value," that's good enough.

Indeed, there may be no such thing as an absolutely correct index for any play, since ultimately each index needs to be computed for every composition of your hand, various game conditions, etc.

For example, you would always hit 14 VS. T, wouldn't you? I don't even keep that index in my arsenal. But what if you are playing single deck, and your dealt 7-7? Then you stand, right? Even when the count is -1 (the two 7's and the T).

Indices are good to learn, but strategy variation is not that important to playing a winning game (especially in multiple deck), and most of the plays you make where you vary are because the count is way above/below the index.

As you can see, your question is one I have thought about before -- I just wish I had a few better analogies to really bring home the point

--Mayor

My additional spin is that, "precise index" is a misnomer if not an oxymoron - I advocate rounded and risk-averse composite (2D algebraic) indices of at least 50+ in number (I started in the 70s when we routinely learned 150-200+ index#s (i#) and still use 100 myself)

Liberal rounding of the i# allows you to personalize your i# pattern for rapid deployment, time is money - secondly, as Mayor has indicated, the difference between hitting or standing with 16v10 at -1 to +1 is of no value - therefore I beleive that the 'coin-toss' wide-borderlines imposed by each of the i# can allow one the opportunity to access less conscious-mind areas of the brain and intuition - perhaps unconsciously we DO likely know that there is one extra 5 or 4 that warrants hitting the 16, or vise-versa, or even "let the force" or whatever have a free reign within the wide-border.

Many BJ posters beleive or strive for precision i#, whereas I opt for "fuzzy-logic" and algebraic (non-sim'd) i#

Also the coin toss can make for a cover play that I have used - flipping a coin to call my play or bet, especially big ones, repeatedly, even chronically, and sticking with the coin's decision (or if the coin is wrong too much, going aginst it, great fun)! zg

INDEX TWEAKS/TERMS -

RA (risk-averse) = alternate index#s (i#) that decreasevariance/flux while resultingly increase EV. A prime example is 10v10. the RA index is higher by 70% approx, same true for 9v2. (Mayor, can you elaborate a bit on the concept of RA i#?)

Composite = a set of i# that reflects a compromise between the slight differences of 1,2,6D i#.

Rounded = i# is liberally rounded for simplicity and ease of deployment. For example 12v2=+5, 12v3=+3, round both i# for all future memory/use to +4. A more extreme yet acceptable approach is to round ALL +1,0,-1 i# to 0, etc.

Algebraic i# = i# obtained thru algebraic approximation rather than computor simulation or extrapolation.

zg

Am I correct, then, to extrapolate from this that if I were to compile a set of indecies that were within 1(or so) of those calculated through the combinatorial analysis, and grouped them in a way that made it easier to remember more of them, I would be in better shape than following rigid index values?

Also, I'm still a little uncertain of the concept of RA.

Thank you all.

-Felix

Many studies have shown you can be off by +1 on almost every index you use and it won't make very much difference overall.

Here is a good tip: if you are going to be off, it is better to be late than early. Example: say an index is +3. Player Late makes the play at +4. Player Early makes the play at +2. Player Late will do better than Player Early, in fact a basic strategy player may even do better than Player Early.

Risk Adverse indexs are useful if you are betting close to an optimal bet spread to the count, and your betting unit is closely scaled to the optimal amount according to your bankroll.

Using RA numbers, you don't alter basic strat and double down or split unless the count makes the move *really* profitable. By not making plays at the *optimal* count, you are giving up some EV or long term profit. However, you are reducing your variance and overall risk or ROR (Risk of Ruin). So, in order to compensate for your decreased risk you can increase your bet amounts or spread, and play with the same ROR without increasing your bankroll size. (Bet more - win more - same risk).

** My responses are embedded -

Am I correct, then, to extrapolate from this that if I were to compile a set of indecies that were within 1(or so) of those calculated through the combinatorial analysis, and grouped them in a way that made it easier to remember more of them, I would be in better shape than following rigid index values?

** I say yes, Kansas has provided addt'l considerations and an excellent addt'l insight into RA i#. Kansas' insights, notwithstanding, do NOT be afraid to round the i# pattern grossly, it won't matter except for increased ease and speed and i# - remember, there ain't no such thing as "precise i#"

zg