Probability in online casino slot machines: Dilemma

Hi there, I am new here, but I have come as I am interested to see what people make of this.

I am part of an online community that collectively complete online casino slot offers that we perceive to be of value. For instance :Stake £20 on slot machines, to get a £5 cash bonus. The house edge for most slot machines is 5%, so on average: For every £100 staked you would expect to lose £5 , so I would expect to lose £1 from the wagering, then gain a £5 bonus. While I can't guarantee I will win, on average I would hope to make £4 (the 'expected value') for every time I complete it.

There is some heated discussion about whether to quit when you are up above the £4 or whether to carry on, and there two sides to the argument, so I would like to see an outside view point on it from people with an interest in stats & probability. I'm an engineer so have a reasonable grasp of maths.

If you had completed £10 of wagering, and you were already in profit by £10 (more than the 'expected value' of the offer, is it better to stop or to carry on? I am a little uncertain as to whether the outcome of the previous spins has any bearing on what will happen with the next spin, but I don't think it does. The counter argument for carrying on is that you would now only have to wager £10 for a £5 bonus.

It would be interesting to hear people's views. Stop or carry on?

Thanks in advance


Mean Joe

TS Contributor
If you had completed £10 of wagering, and you were already in profit by £10 (more than the 'expected value' of the offer, is it better to stop or to carry on?
Why are you gambling? What is the goal of gambling? I think that's a really important consideration, for the individual.

You should have an idea of what your stop point is (both winning and losing).

Beware of being greedy, because you are bound to be drawn down. There is no long run scenario where you can "expect" (using the statistical definition of the word) to satisfy your greed.

The LONG RUN will always say you will lose. So if you were up £10, should you stop? Should you stop forever? How long should you stop? That is why I believe, you should understand your goals in gambling.
Interesting question. I used to work in a casino, but have never gambled myself. Out slot machines were "tuned" to return 98% of the money they took in "over their lifetime" (generally considered to be 7 years).

The house always has a slight edge in odds. It only needs to be a slight edge, because it plays every day, all year, at every table and slot machine. Each day, the net is positive for the house. The greater the volume of gambling that a person does, the closer their results will be to the statistical probability. The only way for someone to really "win" at gambling is to walk in, get up (net gain), and walk out - and never go back.

If you are gambling to make money, it's so unlikely to happen that you would have to be irrational to believe so. If you are gambling because you can afford it and you find it entertaining, that's something else.