The RTP is nothing more than a statistical value that expresses how profitable a slot is for the casino, i.e. how much money on average it earns or the player loses. The RTP must always take a value between 0 and 100%. 0% would mean that the player would never get a cent back – the machine would eat money. 100% means that the slot pays everything back on average. If you bet 100 Euro at a slot you would on average get 100 Euro back in winnings. In this scenario it is obvious that the casino cannot earn anything. To offer this slot would make no sense and therefore it does not exist.
Fortunately, the RTP of normal slots in the high 90% range is usually between 95 and 98%. An RTP of 98% means for example that the player gets back 98 Euro on average if he bets 100 Euro. This is a very good value for the player as slots usually pay out a little worse. That means: The slot with 98% is very fair and a good choice.
Understanding the statistics behind RTP
The problem of many casino players is lack of knowledge about statistics. They quickly refer to a game as “fake” or “rigged” when it runs against them even though everything is within a statistical framework. The RTP itself doesn’t say much about how a slot will behave in the short term. Of course there can theoretically be a slot that always returns the exact percentage. So that you bet 1 Euro and always get 98c back – with every turn. That would be very predictable and boring. Nobody would play at such a machine because there is no prospect of winning.
That’s why a slot can’t be so predictable, so it has to fluctuate around this average/RTP based on the actual payout. Sometimes it pays out after 100 times 1 euro spins only 50 euro, then 200 euro. The next time 90 euro, then 60 euro. Then 20 Euro, then 200 Euro. And so on. It is important to understand that a lot can happen in the short term and with rare assignments. Both in one direction and in the other. An RTP is only the statistical value that will settle down after several thousand sessions. So only if you bet e.g. 10 000 times 1 euro you will be able to say actually how high the RTP is.
Exactly this is the problem with gambling but also something that makes it so interesting. Because only few players have the necessary basic knowledge of statistics and simply assume that a value like an RTP is carved in stone and must be noticeable in every session. That means a player bets 100 times 1 Euro and expects then that on average at least 97 Euro come back. If it is more he does not complain of course, but if it is less he pushes it gladly once on the Casino and/or the Slot.
Traceability of RTPs
This is exactly what makes RTP not easy to understand. Because you have to simulate a game thousands of times to be able to make a halfway exact statement. The RTP which is also published by the slot manufacturers is a calculated and theoretical value. It would still have to be determined in practice. Often it is about such small fluctuations that it is “irrelevant”. Imagine you have a slot with 97.5% and one with 97% RTP. Of course you expect it to bring in more with 97.5% in the long run. But to really notice a difference you have to play a lot with both machines. And even then there is no guarantee that the difference will be noticeable.
It’s different in extreme cases like offline slots which sometimes have a ridiculous 55% RTP. There you will very quickly notice a difference to a 97% slot without having to bet 10 000 times. Often you notice it already after 20 spins because you have very often loss series with such a bad paying slot.
Verification of the RTP by the licensor
The UK Gambling Commission is probably the leader in this field and takes it very seriously. Therefore it’s hard to keep yourself as a frivolous casino. The Gambling Commission has been calling for live RTPs since 2016. The RTPs calculated by the manufacturers may differ from these live RTPs. That is logical, because these are only a theoretical value. So if a casino would try to cheat you will see very quickly that the live RTP is very different. So e.g. instead of 96% it’s only 91%.
What you have to say is that the sample size has to be very large. Here a confidence interval of 95% is calculated, which means that there is a 95% probability that the live RTP differs from the theoretical RTP. A higher probability is hardly possible because one would need much, much larger samples for this and it can take months or years until one can make a statement.
That means: The Gambling Commission wants to see about 400.000 spins to be able to say that a deviation of about 2% is not normal. Simply put: The live RTP is 93%, the theoretical RTP 95%. Over 400,000 spins are required that one can now say that there is a significant difference. Only then would the Commission intervene and complain or ask why such a deviation exists.
You can read more about this topic here.