Interview Questions

What is risk analysis? What does it have to do with Severity and Priority?

Software QA/Testing Technical FAQs

(Continued from previous question...)

What is risk analysis? What does it have to do with Severity and Priority?

Risk analysis is a method to determine how much risk is involved in something. In testing, it can be used to determine when to test something or whether to test something at all. Items with higher risk values should be tested early and often. Items with lower risk value can be tested later, or under some circumstances if time runs out, not at all. It can also be used with defects. Severity tells us how bad a defect is: "how much damage can it cause?". Priority tells us how soon it is desired to fix the defect: "should we fix this and if so, by when?".
Companies usually use numeric values to calculate both values. The number of values will change from place to place. I assume a five-point scale but a three-point scale is commonly used. Using a defect as an example, Major would be Severity1 and Trivial would be Severity5. A Priority1 would imply that it needs to be fixed immediately and a Priority5 means that it can wait until everything else is done. You can add or multiply the two digits together (there is only a small difference in the outcome) and the results become the risk value. You use the event's risk value to determine how you should address the problem. The lower values must be addressed before the middle values, and the higher values can wait the longest.
Defect 12345
Foo displays an error message with incorrect path separators when the optional showpath switch is applied
Risk value (addition method) 10

Defect 13579
Module Bar causes system crash using derefenced handle
Risk value (addition method) 2

Defect 13579 will usually be addressed before 12345.
Another method for Risk Assessment is based on a military standard, MIL-STD-882. It describes the risk of failure for military hardware. The main area of interest is section A.4.4.3 and its children where they indicate the Assessment of mishap risk. They use a four-point severity rating: Catastrophic; Critical; Marginal; Negligible. They then use a five-point probability rating: Frequent; Probable; Occasional; Remote; Improbable. Then rather than using a mathematical calculation to determine a risk level, they use a predefined chart. It is this chart that is novel as it groups risks together rather than giving them discrete values. If you want a copy of the current version, search for MIL-STD-882D using Yahoo! or Google.

(Continued on next question...)

Other Interview Questions