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3.1 We are setting certification standards for an object library that we will use to develop software products in a particular domain. The products must meet a failure intensity objective for severity 1 failures of 10 failures / 1000 exec hr. Previous experience indicates that 10 percent of total failures will be severity 1. We expect that 50 percent of the failures that will occur in the field will be due to incorrect integration of the objects and 50 percent due to faulty objects. Each product will consist of 100 objects. 50 percent of each product will consist of reused objects from the object library. The new objects that we write for a product must meet the same reliability standards as the object library. All objects must work correctly for the product to work. The objects are independent of each other with respect to failure behavior. What total failure intensity objective should we set for each object in the object library?

3.3 The last release of our product had a failure intensity of 100 failures / Khr. It took 1 year to develop and cost $2 million. There were 10 principal operations. The next release will add 10 new principal operations of similar size. In the new release, the operations from both old and new releases will all have equal usage. We must deliver it in 1 year and reduce the average failure intensity to 90 failures / Khr. What can we expect the approximate cost of the next release to be?

3.4 Our new copier must not fail more than once a week. Average daily use during the 5 day work week is 2,000 copies / day. Field data indicates that we can expect one mechanical failure every 25,000 copies. What must we set as the failure intensity objective for the copier software we are developing?

3.5 Can you give an example of a “failure” and the related “fault” from your project?

 



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