There is of course no telling when a slot machine is going to award its bonus game, unless you play one of the Feature Guarantee slots from Real Time Gaming. Those slots have a spin countdown meter on which as soon as the countdown reaches 1 you are guaranteed to be awarded a bonus game on the next spin.
However, those slot machines are not to everybody’s liking and as such you may prefer playing one of the standard video slots on which it will always be a surprise when the bonus game has been awarded to you.
As for how you can actually work out when a bonus game on average should be awarded to you, well you will need to dissect the reels and work out just how many reel symbols are on each reel and also discover just how many of them are scatter or bonus symbols.
That can of course be very difficult to do, much more so when playing online slots, but that is something that I have been able to do, and as such I set about trying to work out just which of a large range of slots I played is much more likely to awards its free spins feature round more than others.
It is the Halloweenies slot that is the one that does tend to award its free spins feature more often than most other slots, for on average it should take around 76 base game spins until you spin in three of the scatter symbols which then awards 13 free spins which all play off with x3 multipliers attached to them.
So if you do enjoy playing slot games online, and want to have a very fair and reasonable chance of triggering a set of free spins then it should be the Halloweenies slot you get stuck into playing!
Just make sure that the casino you play at is licensed by a respected gaming authority or gambling commission and one that is licensed in your country of residence too!