Some users however may be the
customer??™s customers. Some user types (such as system administrators and operators) may be common
across customer types.
At this point it should be possible to generate a table like the one shown in Table 7.4.
TABLE 7.4 Sample user profile
User group
Customer group 1 probability = 0.6 Customer group 2 probability = 0.4
Total
user group
probability
User group
probability within
customer group
Overall
user group
probability of
customer group
User group
probability within
customer group
Overall
user group
probability of
customer group
Public users 0.900 0.540 0.900 0.360 0.900
Operators 0.070 0.042 0.050 0.020 0.062
System administrator 0.010 0.006 0.035 0.014 0.020
Support desk staff 0.020 0.012 0.015 0.006 0.018
Testing Processes and Infrastructure 111
7.7.3 Establish Risk Levels
Risk is simply the probability of something happening multiplied by the cost if it does. Each outcome
of the system will have a risk associated with it. In the case of Word the failure to print a document
correctly could be catastrophic if airline pilots depend on that document for their wing de-icing profile
or if that document is used by railway signalers to determine which parts of a railway system are
???possessed??? by a railway company to run trains on and which are ???possessed??? by railway maintenance
staff carrying out permanent-way repairs.
Each feature and mode in a system will thus have a risk level.
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