Describe the difference between known risks and predictable risks?

Known Risk :

1) It can be uncovered after careful evaluation project plan, business and technical environment in which the project is being developed, other reliable information resources.

2) E.g. unrealistic delivery date, lack of software poor development environment.

Predictable Risk:

1) Predictable risks are extrapolated from past project experience.

2) E.g. staff turnover, poor communication with the customer, dilution of staff effort as ongoing maintenance requests are serviced.