Scepticus, there are different types of biases...
Vb itself is a part of bias play. In case of Vb we assume presence of drop point bias or track bias.. ets.
To play seriously need to achieve high confidence factor, it's math limit beyond wich phenomenon observed starts to be statistically significant. For example, you can see in 10 spins ball coming 6 times to same diamond, but you will need at least 50 spins to confirm such ratio.... if you wanna be sure, 150 spins...