Question

Quality control for Comfort-Ease Computer Peripherals, Inc. has done studies showing that its voice
recognition device has a mean life of 7.5 years with standard deviation 2.2 years. The manufacturer will
replace any such device that wears out during the guarantee period.
(a) If the guarantee period is 5 years, what fraction of the voice recognition devices will the
manufacturer have to replace?
(b) How long should the guarantee run if the manufacturer wishes to replace no more than 10% of the
devices?

Answer 1