A Percentage Role is a role with a modifier stating that they only work as stated a certain percentage of the time. For example, a 50% Doctor (also called a Faith Healer) will protect their target 50% of the time and be completely ineffective the other 50% of the time. The player is not explicitly told whether their role worked.
Occasionally moderators may tell the player whether their role was effective.
The percentage of the time that the role works can vary. It may not even be stated to the player; instead the modifier will appear as 'Random'.
In very rare cases the player will not be self-aware of the percentage aspect of their role.
Information roles may or may not be told whether their ability worked. For instance, a 50% Cop whose ability did not work may be told their ability did not work, or they may receive a default answer ("Not Guilty" or "No Result", for instance). Roles that have the possibility of returning No Result normally, such as Tracker, will generally not be told if their ability did not work.
Schizo is similar to a percentage role.
Roles that work 0% of the time may also be called False Roles.
Use and Power
Percentage roles are extremely unpopular due to incorporating a large and uncontrollable element of luck to a game, potentially negating any skill the player with the role may have. In extreme cases percent-based roles may be seen as an excuse for the moderator to toy with the players. It is recommended in most cases that percentage roles not be used at all, as many players associate it with bastard modding.
For obvious reasons, this modifier lowers the power of any ability it is attached to.