If it's really a 20% chance, and you do it enough times, the actual results should show something very close to 20%.
The question is, what is "enough times" to prove the 20% out? It's not going to be measured in 100's or even 1,000's. Any statisticians care to answer that?
In order to have any chance to prove/disprove it would take an exhaustive effort, to either get the entire server to co-operate and provide their results for an entire day worth or RE results, or take a server where you have unlimited access to things to RE and are the only person on the server. Good luck finding that amount of co-operation in this community, b/c you are not going to get the second option.