What is slot machine dispersion?

There is an interesting notion applicable to gambling, which is called “variance of random variable”. According to the widespread description, it is a measure of spread of the given random value, in other words, a range of deviations from its theoretic average. Remarkably, this notion became popular in reference to poker.

So, let us take a closer look at dispersion. The notion itself was initially coined, applied, and used in the theory of chances. Dispersion is interpreted as a mathematical deviation from the estimated mathematical expectancy of any event. Does it affect the whole result? A vivid example: imagine you toss an ideal coin that does not have any scuffmarks or notches. According to the theory of chances, a coin tossed twice, is going to fall “heads” for the first time and “tails” for the second time. So why does it fall down in a completely different way? The answer is quite simple: because the expected result is predetermined by dispersion. When it actually comes to slot machines, we are referring to variance of random variable.

Variance of random variable is a measure of spread of the given random value, namely, those are deviations from its mathematical expectancy μ. It is usually represented by D [Х], but English and Russian reference books also denote it as Var (Х), descending from the English word «variance». Statistics denominates such signs as σ2X or σ2. Square root out of dispersion equal to σ, might be called as
root-mean-square deviation, or standard deviation or standard scatter. Standard deviation is measured in the same kind of units as the random value itself, while dispersion is estimated via raising those units to the square.

Let’ s consider density of the probability distribution of the final result according to the extent of dispersion, provided that the red curve line corresponds to normal distribution. As one can see:

  • Characteristics of the curve line are determined by two main factors: μ and σ;

  • Statistical expectation μ of the random variable Х determines the center of dispersion;

  • Dispersion σ determines the measure of dispersion of the Х value in relation to the center of dispersion.

In other words, “dispersion” means «scattering», that´s why dispersion characterizes “sparsity” of the value of a random variable in regard to its expected value.

Low dispersion value, as can be seen from the graph, points to good results. That’s why depending upon the scope of dispersion, slot machines can be divided into three main types: highly dispersive, moderately dispersive and those of low dispersion.

Let us take a closer look at how all of those factors influence winnings.

Highly dispersive, moderately dispersive and low dispersion slot machines

  • Highly dispersive slot machines rarely come up with winning combinations. Anyway, the bankrolls are enormous and the total winning amount is substantial. These slots are popular predominantly among people who have enough time, patience and huge bankrollі while fishing for big prize money.

  • Moderately dispersive slot machines are characterized by medium gambling gains that basically do not take long time to get. Such slots are good for the gamblers who do not have huge bankrolls and prefer not to wait for too long in order to get their reward. However, these people won´t settle with pitiful payoffs.

  • Low dispersion slot machines stand out particularly due to the high probability of winnings and high percentage of winning combinations. However, the payoffs, usually, are not higher than regular stakes. These slots are generally popular among gamblers who are into dynamic gameplay, thrill of the race, instant winnings and doesn´t have substantial bankrolls.

How to determine volatility of a slot machine

Traditionally, slot machines providers, needless to say, online casinos, do not indicate the scale of dispersion in the descriptions to their slots. However, this is one of the most significant parameters that influence the frequency and the amount of prize money. Now let us move forward to the question how average gamblers grapple with different slot machines in terms of their volatility.

In the professional gambling circles there are a couple of parameters serving as slot classifiers. A slot with a payoff index higher than х10000 is considered to be highly dispersive. If this index ranges from х5000 up to х10000 the slot machine is determined as a moderately dispersive one. Low dispersion shows payoff indexes lower than х5000.

There are three main approaches to identify dispersion of a slot machine:

  • The first one and the most effective way is to make a research on payoffs statistics of every single slot machine. This information is publicly available , as well as the rules of the game.

  • The second approach implies personal testing of a slot machine. Currently, many of the slot machine providers and online casinos offer free test trials in order to give gamblers an opportunity to check out the slot. In this case, gamblers estimate first-hand the approximate payoff levels and make their own conclusions regarding volatility of a slot machine.

  • The third approach is connected with reviewing various gambling studies, coverage papers, and forums. More often than not, gamblers share information on different informative resources.

Further actions of a gambler are determined by his/her aims and possibilities. If the main target is to “hit the jackpot”, and there is enough money and time to wait for the bad streak of losing combinations to pass, one should opt for highly dispersive slot machines. If you are not really interested in the jackpot and do not want to jeopardize the whole thing, choose moderately dispersive machines. In case of not having big amounts of money to start with or you do not want to take risks, but you are willing to play and win, select low dispersion slots.

Classification of slots recommended by Slotegrator according to their volatility

Slotegrator is one of the leading providers of quality gambling content for online casinos. Among our partners, you may find worldwide - famous developers of slot machines that have already proved to be the best players on the market offering innovative and top-grade products. The following table provides you with a list of popular games, categorized into three main groups such as: highly dispersive, moderately dispersive and low dispersion games.


Highly dispersive games

Moderately dispersive games


Low dispersion games

An Austrian company Amatic

Book Of Aztec, Book Of Fortune, Hot Diamonds


Diamond Cats, Admiral Nelson, Bells On Fire


Eye Of Ra, Fortunas Fruits, Allways Fruits


A Scandinavian provider of slot machines known as Netent

Dead or Alive, Gonzo's Quest, Jack and the Beanstalk


Koi Princess, Guns N' Roses, Steam Tower


Starburst, Hook's Heroes, Pyramid: Quest for Immortality


A Czech company Endorphina

Jetsetter, Satoshis Secret, Gems & Stones


Ninja, Pachamama, Urartu


Safari, Blast Boom Bang, Ultra Fresh


An English provider BetSoft

At the Movies, WhoSpunIt Plus, Rook's Revenge


Birds, Aztec Treasures, Tycoons Plus


Alkemor's Tower, Fruit Zen, 2 Million B.C.


To sum up, it should be said, that volatility of the slot machines determines the risk levels while gambling. It also predetermines the frequency and amounts of prize money won by a gambler. That is why before starting to gamble, one has to be aware of the volatility factor while choosing a slot.