The probability of failure depends on who is asking [implantable biomedical devices]

There are occasions when an implanted product which is on the market starts to show an unacceptable failure rate or mode of failure. Inevitable questions arise about the number and frequency of failures in this population of patients. This paper discusses the methods available statistically to examine the problem when the rate of failure is low but unacceptable. The estimate made is highly influenced by the reason for the requested estimate.<
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