Slot Machine Odds in Las Vegas

Excluded Casinos

The Suncoast and Rampart Casino in Summerlin do not allowplaying slots and taking notes at the same time. I can notinclude any casino that prohibits the method in which Igather data.

Location Averages

The next table shows the average return by location.

The above sign can be found across the street from thePalms. Although I did the study Anthony Curtis published itin the LasVegas Advisor , which is how it become well known. The"..." in the sign encompases quite a bit of information,which was conveniently left off the sign. Actually the studyonly says that the Palms had the lowest nickel video slotsof the casinos surveyed in Las Vegas. The small print at thebottom says, "Independent study conducted between November2001-February 2002 on Austin Powers, Fortune Cookie, Reel'em In, and Wheel of Fortune games. They left off LeopardSpots, and the study began in October.

Observations

There seemed to be no truth behind slot placement myths.Machines on the end of a bank did no better on average thanthose in the middle. There was also no correlation betweenreturn and proximity to such things as the main door, tablegame pit, high traffic areas, and low traffic areas.

Most casinos were very consistent in their slot returns.If one nickel machine had a return of x% then all otherslike it also returned x%. However some casinos did mix uploose and tight machines, most notably Treasure Island andthe California casinos.

Methodology

A kind and anonymous source provided me with PAR sheetsfor the games in question. The EPROM (Erasable ProgrammableRead Only Memory) chip is what tells the machine the orderof the symbols on the reel, in some cases how the stops areweighted, how much each winning combination pays, and anyother pertinent information about how much the machine pays.It is up to the slot manager to select which EPROM chip toorder according to the return percentage desired. On atypical game there might be about 8 different possiblereturn percentages, ranging from about 85% to 98%.

Each of the different PAR sheets has five sets ofdistinct reels. On video display slots the stops are notweighted; in other words all stops are equally likely. Thedistribution of each symbol on each reel is what determinesthe theoretical return of the machine. For example a higherpaying machine may have more of the higher payingsymbols.

On the machine itself three consecutive symbols arevisible on five different reels. By comparing actualobservations of results to the PAR sheets it is possible todetermine which reels the machine uses, and thus which PARsheet and which return. There are various three-symbolcombinations that appear in at least one but not all PARsheets. So if one of these combinations occurs on an actualmachine it narrows down the possible PAR sheets. By playingenough the player can narrow down the possible PAR sheets tojust one.

To help identify the unique combinations I wrote acomputer program for each game, which had the exact reelorder of all 5 reels of all the PAR sheets. The program thencounted the number of PAR sheets with each possiblethree-symbol combination. If the number was greater than 0and less than the maximum then that combination wasidentified along with the associated PAR sheets it belongedto.

It is then a matter of simply playing the game andcomparing the outcomes to the list of partially uniquecombinations. It only takes about 5-10 plays per machine tonarrow down the possibilities to just one PAR sheet.

The averages in the table are actually an average ofaverages. For each kind of machine at each casino I took anaverage return. Then I took the average of these averagesover the five kinds of machines I tested for.

"Slot Machine" Definition

There is some confusion about what constitutes a "slotmachine" or "slot." My definition, and that of mostgamblers, is a gambling machine with either actual spinningreels or video representations of the them.

People in the gaming business and regulators generallyrefer to a slot machine as any gambling machine, includingreeled slots, video poker, video keno, video blackjack,etc.. For purposes of statistics both casino managers andregulators combine all the electronic gambling machinestogether. For example, reportssuch as the one by the state of Nevada and the SlotChart in Casino Player magazine do not isolate just reeledslots but consider all electronic games a "slot." Thereforemy return percentages should not be expected to agree withthose reported by the casinos or regulators. As far as Iknow mine is the only source to isolate just the return ofreeled slots.

Acknowledgements

I would like to thank Rob Feldheim for helping with theslot play and record keeping. Rob helped me with most of thecasinos on the east side of town and part of downtown. Iwould also like to thank Par Sheet Pete (not his real name)for providing the par sheets, without which this projectwould not have been possible.

Articles

The main-stream media has covered this study in depth.Here are links to some articles.

Turning'em loose , an article that appeared in the Las VegasReview Journal on May 19, 2002, about the possible effectsof this study.
Specifications,computing help crack payoff code , an article thatappeared in the Las Vegas Review Journal on May 19, 2002,about how I did this study.
One-ArmedBandit or Robin Hood? , an article by myself forContingencies Magazine explaining the methodology, results,and weaknesses of the study.
Sheratonslots atop list of nickel video payouts , an article thatappeared in Memphis' The Commercial Appeal on September 15,2002 about how this study was used to rank the Tunicacasinos.
Play by the rules and the one-armed bandits will still win . Boston Globe article about slot machines, in which my Las Vegas survey is mentioned and my advice quoted. (cache)

My Slot Machine resources

Go to slot machine appendix3B (Jean/Primm slot returns).
Go to slot machine appendix 3D(Henderson slot returns).
Go to slot machine appendix 3E(Las Vegas quarter and dollar slot returns).
Go to slot machine appendix 3F(Montreal slot return).
Go back to slot machines.