What are the chances of effects happening?

The BRUTAL skill says it has a chance to apply SILENCE or STUN, last 3 seconds.

What’s the chance of the SILENCE or STUN?

Same thing with EROSION skill, it says there’s a chance to apply [receive 30% SKILL ATTACK damage every 0.5 second(s), last for 3 second(s)]. What’s the percent chance to apply?