getProbability()
getProbability(null|integer  $precision = 10) : float
                        Generate a probability format float number between 0.0 and 1.0.
Note: Passing null will use the global system precision value.
Parameters
| null|integer | $precision | Rounding precision (default => 10). | 
Throws
- \Exception
- Validation errors. 
Returns
float —Randomly generated probability value.