What Makes You Like One Slot Machine Better than Another?

11 May 2005

By Alan Krigman

If you play the slot machines a lot, you're apt to have one or two favorites. What is it about a particular device that makes you like it better than an alternative across the aisle or in a different casino? That, in fact, keeps you returning, not to the slots in general but to the same game, on a fairly regular basis?

An abundance of answers is obviously possible, depending on your personal preferences. Anything from the thrill of trying for a super-high jackpot, to having won big or seen someone else do so on a certain game previously, to a tip from an "insider" about a machine with an especially high "return percentage." You might even actually enjoy one or another of the mindless "themes" the factory sales people tout as being so important nowadays.

Many folks are strongly influenced by positive reinforcement. One form this may take involves the machine's "hit rate," the average fraction of spins which yield any return whatever. Another has to do with the chance of being in action long enough so you still deem your dough well spent if it diminishes rather than grows. These are statistical quantities based on the probabilities of various outcomes. Solid citizens aren't normally privy to such data except in video poker. But, over time, frequent players form intuitive notions about both items. They develop a sense of whether a machine seems to have extended cold streaks or bangs out returns encouragingly often. Similarly, absent a big win, experience if not accumulated "points" tells them whether a game gives them a fair shot or just drains their fanny packs dry.

It turns out that the bosses who specify slot machines have some flexibility in setting these two parameters, even while holding the overall return percentage constant. Those who understand how to use this can adjust the games to please the types of patrons they want to attract, while still keeping a specified edge and earning the desired average fraction of the money wagered.

The principle is illustrated in the accompanying table. This shows the chances of various returns on each spin of four hypothetical slots. The machines would show identical payoffs on their belly glasses. And they'd all return a nominal 95 percent of the money wagered, earning the casino the other 5 percent. A virtually unlimited range of other combinations is conceivable.

Payoffs and probabilities for four hypothetical slot machines,
all returning a nominal 95 percent of the money wagered

Return	Machine 1	Machine 2	Machine 3	Machine 4
0	75%	75%	65%	65%
1	13%	18.34%	18.98%	21.67%
2	6.19%	3.67%	9.03%	10.32%
5	2.95%	1.75%	4.30%	2.16%
10	1.40%	0.01%	2.05%	0.01%
25	1.40%	0.83%	0.63%	0.57%
100	0.06%	0.40%	0.01%	0.27%

Were payback percentage or edge the only criterion characterizing performance, the four machines would be equivalent. They're not, at least not to players. Machines 1 and 2 lose an average of 75 percent of all spins and hit on only 25 percent. Machines 3 and 4 are expected to lose an average of 65 percent and hit on the remaining 35 percent. If you're easily discouraged by strings of misses, you'd tend to favor machines 3 and 4 over 1 or 2.

There's more. Say you start with a $100 stake and bet $1 per spin. On machines 1 and 3, you'd have 38 and 50 percent chance, respectively, of still being in action after two hours at 600 rounds/hour. Machines 2 and 4 have 26 and 30 percent likelihood of sessions this long, respectively. If you hate to blow your bankroll in short order and spend the next few hours pretending you're not sorry for visiting the casino instead of your in-laws, it's a good guess you'd fancy machine 3 over the others.

Players for whom hit rate and prospects for an extended session, together, are of primary importance would gravitate toward machine 3, of the choices presented. This doesn't make the game better than the others in any absolute way. For instance, hit and survival rates are maximized in this case by accepting the lowest chance of winning the 100-unit jackpot. A manifestation of the maxim memorialized by the immortal muse, Sumner A Ingmark:

When you think you've beat the system, don't be proud,
Though believing foolproof theories is allowed,
In truth, every silver lining has a cloud.