The four word term probability and impact matrix sounds like something terribly complex and difficult to understand but in reality is something that when understood is an extremely simple concept and something which is practiced not only in the arena of project management but also by most people in their everyday lives. Specifically, the concept of the probability and impact matrix refers to instances in which the project management team and or the project management team leader determines that there is a certain element of risk involved in one or more phases of a project or of an activity that is a part of the project as a whole. The probability and impact matrix refers specifically to the means that the project management team and or the project management team leader determine exactly what those risks may be. In using the probability and impact matrix, it is determined whether the risk would be classified as low, medium, or high, by considering two distinct factors: the overall probability of the occurrence, as well as the presumed impact if it did occur.
This term is defined in the 3rd and the 4th edition of the PMBOK.