There's a large subset of my email that comes from slot players who start by saying, "I get that the games are random, but …"
Then they tell of a slot experience that doesn't seem quite right to them.
The latest came from a reader named Barb, who said she played the same games at different casinos.
"I love those Hangover slots," she wrote, "but when I play at one casino, I win pretty good, and at the other I NEVER win. I have my losses at the 'good' casino, too, but I get enough back to keep me going. All the symbols are the same, and the pay tables look the same. But it seems like I'm getting 95 percent at one casino and only 65 percent at the other. Do they have different random generators?"
What's probably happening is just that she's had bad luck at one casino, and good luck at the other. A machine that's set up at 90 percent payback doesn't have to pay 90 percent to every player, every time. You might get 63 percent, I might have a session where I get 55, someone else might get a big payback and leave with an 800 percent return.
Through hundreds of thousands of plays, the wins and losses will balance out. The odds of the game will lead to a return very close to the targeted 90 percent, and the casino will take its 10 percent.
Most likely, by pure coincidence, Barb has had a few good sessions at one casino, and a few losers at the other.
However, slot manufacturers do produce random number generators, or RNGs, that will lead to different long-term percentages on the same type of machine, and it's up to the purchasing casino to choose which they want installed.
It's not as extreme as Barb suggested. All states with legal commercial casinos have minimum legal payback percentages - 83 percent in New Jersey and Indiana, and 80 percent in a number of states. Nevada has one of the lowest legal minimums at 75 percent, although competitive pressures lead casinos to pay much higher percentages.
There is no 65 percent chip available to licensed American casinos. But a range of returns is offered, with casinos typically putting higher payback percentages on higher denomination machines. International Game Technology, for instance, makes its big hit, The Dark Knight, available in versions that range from just over 86 percent to about 95.5 percent. WMS Gaming's Attack From Mars/Revenge From Mars ranges from 86 percent to 94 percent. Bally's U-Spin game, Vegas Hits, is available in a range from 86 to 96 percent.
Casino operators look at the detailed information provided by the manufacturer, including not only payback percentage but hit frequency and frequency of jackpots, and decide which version to offer players. There are differences from casino to casino, but the difference in choices usually falls within a narrow range. On a penny slot, it's rare that a casino would choose a payback from the top of a game's range. You're not going to go from an 88-percent game to a 96-percent game at the same coin denomination when moving from one casino to another.
More common would be an 88-percent version in one casino and a 90-percenter in another. In short sessions, a player would scarcely notice the difference. Over a longer period, the biggest effect would be that your money would last a little longer, for more time on device, on the higher-paying game.
So yes, it was possible Barb was playing games with different RNG values. But more likely, the biggest difference was in random luck.
Every time I write about slot machine payback percentages, I get follow-up emails wondering just how the percentages are calculated.
What we see in states that make percentages public are based on casino-wide totals. A report that a casino's penny slots returned 88 percent means that 88 percent of all wagers on all penny slots in that casino were returned to bettors as paybacks.
That leads to a question I received most recently from a Colorado reader: "If the percentages are based on actual bets and payouts, how can a machine have a payback percentage before it's even installed?"
The payback percentage that is advertised to an operator deciding whether to install a game is a theoretical payback percentage. That means the odds of the game have been set up so that long-term play, over hundreds of thousands of spins, will yield something very close to that payback percentage. Just as the odds of roulette have been set so that in the long run - the house will keep 5.26 percent of wagers - odds are set on a slot machine that will lead to a desired return.
Some players win, some lose, and in the long run the house collects its percentage.
Gambling author and columnist John Grochowski's weekly newspaper column began at the Chicago Sun-Times and is now syndicated nationally. He also regularly makes TV and radio appearances about gambling. His column appears weekly.