Index number: Question for some of the pros out there

I am still a little confused about the right index numbers. I first memorized the index numbers out of Stanford Wongs book Blackjack Secrets located on pgs. 46-59. The book stated that when using the tables you needed to truncate and not round. Then I read Don Schlesingers book BJA3 and he had a similar but slightly different set of index numbers. In his book he stated that the index numbers were floored. Now I understand the difference between the two meanings but to my understanding that would mean that only the negative index numbers would differ on the two charts. In this case some of the positive index numbers are the same while some of them are one off.

For example in Wongs book 12 v 3 you would stand if you had a count of 1 or higher. In Dons book you would stand if you had a count of 2 or higher. Shouldnt thoes be the same no matter if you truncate or floor?
In Wongs book 13 v 2 you would stand with a count of 0 or higher and in Dons book it is a -1.
Then in Wongs book for surrender 15 v A would be surrendered with a count of 2 or higher. In Dons book it says 1 or higher.

I am just trying to figure out why some of the numbers would be different and some would be the same. Like I said before I understand the difference between truncating and flooring but as far as I knew that would only apply to positive numbers. Am I just not using the right wording or what? Any insight to these differences would be greatly appreciated. Also the wording used to describe the index number for example hit if less than or stand if equal to or higher. Thanks alot for the help this has been quite confusing for me.

See http://en.wikipedia.org/wiki/Floor_function

Consider 13 vs 2. Suppose the actual index value would be -0.5. Truncate and you get 0. Floor and you get -1. So that may explain 13 vs 2, but it doesn't explain the other discrepancies you mention, since flooring and truncating are identical for positive numbers.

Personally I find multiplying easier than dividing. So I MULTIPLY the index number by the number of decks remaining (rounding to nearest half deck), then compare the result to the running count to make the playing decision.

Maybe that works fine for some systems but not for others.

Your assumptions are all correct. The reason Wong's numbers aren't all identical to those found in BJA3 (which were generated by Norm's simulations) is that Wong didn't use the same methodology that Norm did.

And, with today's computers and simulation capabilities, we like to think that the numbers found on p. 213 of BJA3 are the most accurate that can be generated for Hi-Lo.

But, to my knowledge, none differ from Wong's values by more than one, and, from a practical point of view, you may use either, and it will make virtually no difference at all in your final results.

Don

Thanks alot Don for clearing that up for me. That was a big help.

Patterson