[net.math] lotto odds

denny@beesvax.UUCP (06/16/83)

The problem with buying all of the numbers for the lotto game is what happens
if there are multiple winners.  Since the payoff is probably split evenly
among the winners the expected return on the 'investment' is less than you
would think it is.  If there was a way to find out the numbers that are not
played by anyone and purchase these numbers when the jackpot is greater than
$1.9 million, then the odds are in your favor.  The only trick is to obtain
this information.

There was a mention to something similar to this in the math games section
in Scientific American some time ago.  The general idea was to buy 'unpopular'
numbers in a parimutual type state lottery.  The idea of this was that the 
payoff was greater than the odds.  According to the article it is possible
to determine certain numbers that are not played or seldom played.

leichter@yale-com.UUCP (06/17/83)

For some interesting information on these games, see "Lotto Baloney" by Curt
Suplee in the July 1983 Harper's.  Quote:  "You're seven times more likely to
be struck by lightning than to win the state lottery."
							-- Jerry

wdr@security.UUCP (William D Ricker) (06/18/83)

We have a very similar game in Massacusetts called MegaBucks.  The
state picks 6 numbers from 36 without replacement.  Having picked all 6
on your betting slip, you win the Jackpot, minimum $400,000, paid over
20 years (present value =~ 1/2).  Additional prizes are given for 5
numbers and 4 numbers, with a free bet given for 3 numbers.  These
prizes are small potatoes, but add tremendously to the 'expected
value'.  Bet is $1.  Unclaimed jackpot money rolls over to next
jackpot.  Player pool expectation is 50%.

The state commission has also recently distributed coupons worth
a free bet and 25 cents off a bet.  I'm saving my free bet untill
the jackpot gets good and full.

The expected value calclution which I made when they changed the game
to $400k+, 6/36; from $200k+, 6/30; resulted in even odds when the
jackpot was $1.9m.  For the $200k+, 6/30 game it was $.9m.  Both of
these calculations assumed "If the bettor wins the Jackpot, s/he will
be SOLE winner", as the jackpot is split by multiple winners.

The massachussestts commission by law pockets 50% of the gross, less
any deficit in a minimum jackpot ($400k) game.  All gross over the
state cut and the mandated prizes (I think $400 and $40, they used to
be $200 and $20, for 5/6 and 3/6) is placed in the jackpot.  Unwon
jackpot funds rolls over to next week.

------------ ANALYSIS

The analyses on the net, taken as a whole are accurate.  The state will
not lose money to syndicate play because:

	(1)  Multiple winners of the Jackpot split the prize;

	(2)  The jackpot is payed over 20 years.  They could offer a
	jackpot equal to the entire take payable over 20 years and
	still pocket half the gross (after office costs) if they didn't
	have other prizes.  My estimate of the states cost for 19 year
	annuities specs very close to that.

	(3) In the Massachusetts game at least, the jackpot is limited
	to 1/2 the take less other prizes (?less 1/2 expenses?).  only
	if revenue (gross, or 'action') falls below $.8m, does the
	state loose money.  The state may actually loose money if on
	the first week of a new jackpot there is insufficient 'action'
	and someone wins.  Of course, if there is less than $.8m of
	action and they have to pay the $.4m prize (cost=$.2m), they
	are still have upto $.2m to payoff incidental prize winners
	before touching the profit, er, revenue.  On a light betting
	week it is not likely that there will be a BANKRUPTING run of
	small bets to pay.  They probably have occaisional weeks where
	the net take is less than 50%.  I don't know if they absorb
	that loss or take it back from the next rolled over jackpot.
	On weeks with a BIG jackpot, there is PLENTY of action, but
	most of the prize money is SURPLUS prize money from previous
	weeks.  The state alread got its 50% off the top of the rolled
	over jackpot.

             Bill Ricker 
		(617) 271-3725
             wdr@security.UUCP                                      (Internet)
{allegra,genrad,ihnp4,utzoo,philabs,uw-beaver}!linus!security!wdr	(UUCP)
	wdr@mitre-bedford						(ARPA)

chris@grkermit.UUCP (Chris Hibbert) (06/20/83)

The following article appeared in the April '83 Issue of "Software
Engineering Notes, an Informal Newsletter of the ACM SIG on Software
Engineering".  I couldn't find a copyright notice, but the usual notice
in ACM SIG publications is something like: 

"Copyright 1983 by the Association for Computing Machinery, Inc.
Copying without fee is permitted provided that the copies are not made
or distributed for direct commercial advantage and credit to the source
is given."

			Fronton-Center Tickets for the Pick-Six Papers

In case you missed the brute-force example of almost-fail-safe
betting in the papers on 10 March 1983, it bears mention here for its
implications on fail-safe programming.  In Palm Beach Pick-Six
Jai-Alai, the jackpot payoff results from picking the winner of six
games each of which has eight teams competing.  Thus, there are 8**6
= 262,144 possible outcomes.   (The outcome of each game is  naively
thought to be relatively random, although years ago I did a little
calculation showing that there are surprisingly significant
probabilistic biases due to order -- even given equally matched
opponents.)    If no one gets all six winners exactly right, 25% of
the pool is split among the closest pickers, and the remaining 75% is
added to the jackpot payoff-- which accumulates.  On this occasion
the jackpot had gone untouched for 146 consecutive events, and had
built to $551,331.  A well-organized group of people placed 262,144
different bets ($2) -- covering every possible outcome at a cost of
$524,288.  The resulting payoff was $988,326.20 (the night's pool
[minus the fronton cut] plus all of the accumulated jackpot).  Thus
success depended critically upon no one else picking the winning
combination.  Even a two-way split resulting from a competing winning
ticket would have resulted in a $30,000 loss. (An off-night had been
chosen on which a small crowd would normally be expected to place
only about 10,000 bets -- covering a somewhat lesser number of
distinct combinations, with some replications.)  Well, you may ask,
what does all this have to do with software engineering?  The moral
of the story is that if superficial analysis shows you have covered
all your bets, you may still lose your shirt.  How do you ensure that
you got a ticket for each combination?  What if the ticket seller
dropped one [out of 262,144<!>] on the  floor?   What if the
equipment malfunctions in the midst of betting?  What if you don't
finish placing all the bets in time?  (The process is still largely
manual , but now deserves an indivisible transaction "BET * * * * *
*".)  And now that this exhaustive strategy has been used
successfully, you also have to beware of someone else trying it on
the same evening as you!  Worse yet, if it were easy to make the
power-set bet, then you could probably not detect that someone else
was trying the same exhaustive strategy -- which tied up betting
counters for about half an hour at Palm Beach.  "Expect the
unexpected" is an adage given to system designers and programmers,
urging them to anticipate every possible unusual event.  But, as we
saw in the ARPANET collapse [Eric Rosen, SEN Vol. 6, #1, January
1981], for example, that means anticipating hardware problems as well
as algorithmic problems.  [I note in passing for those interested in
proving fault-tolerance properties that the word "admonish" means "to
reprove for a fault".]