That's NOT how probability works. Just because you have a 50-50 chance of flipping heads does not mean it only takes two try's to get heads. On AVERAGE it does.
Yea, I think even if people know this they don't intuitively grasp how far off they are. Five tries at 20% success rate is only 67% overall. That's about the same odds you have to win two rounds of russian roulette.
To have an overall 99% chance (what we might conversationally say is a guarantee), it'd take 21 tries.
To have an overall 99% chance (what we might conversationally say is a guarantee), it'd take 21 tries.