
16 Improving reliability and quality for product success
Since using the MTTF as a lifetime index breeds misunderstanding,
it should not be equated with lifetime. Clearly, the BX life index more
appropriately reects the real state of product reliability.
*
Note that its
inverse becomes the failure rate. The inverse of 20 years is an annual fail-
ure rate of 5%, which conforms with Table2.2.
The reason for extending the lifetime to 20 years is that lifetime is
calculated under the assumption that product failure is random. The
annual failure rate of 1% for rst-class home appliances is converted into
an MTTF of 100 years, ...