Range for of risk probability and impact ratings ( Risk )


Hi, I ran into this question from a simulation exam ( from SSI Logic ). Please see the explanation for the answer below the questioin.  I thought the answer would have been 'A'. I was not aware that the ratings were between 0 and 1. In Rita Mulcahy's PMP Prep Exam book she lists them from 0 to 7. And I believe according to the PMBOK this can defined to meet the project needs. Can someone expand on this?

 

Question:

The Risk Management plan will usually contain the definitions of risk probability and impact.  Which of the following has the highest impact (negative) on a project?

A.  A rating of 1.1 on the impact scale.

B.  A rating of 0.8 on the impact scale

C.  A rating of 0 on the impact scale

D.  A rating of 0.1 on the impact scale

[The impact scale will contain the probabilities of certain risks occurring, and will contain values from 0 to 1.  A value of 0 indicates non-occurrence of the risk while 1 is a certainty.  Hence, a risk impact of 0.8 represents the highest impact among the choices presented.  (PMBOK  Page 281 – Risk)]

Probability of any event occuring/not occuring always varies between 0-1.  A simple way to remember is like % you can score in an exam varies 0% - 100%.  Choice A is ruled out as you can not score 110% since the maximum is limited to 100%.  Pl. refer to PMBOK 4- 11.3.2.2 Figure 11-10.  You assign/estimate the probability of an even occuring; You also assign its impact again as a %.  You multiply these two to estimate the net impact.  The higher the number - the greater is the priority needed to act on.  Choice B shows 80% impact which is greater than choice C & D and is practically possible as it falls with in the max. allowed 100% - hence it is the right choice


Chandra