Assume that the failure rate calculated in Problem 6.41 is unacceptable.
(a) To what value would the standard deviation of shaft strength have to be reduced in order to give a failure rate of only 3%, with no other changes?
(b) To what value would the nominal shaft strength have to be increased in order to give a failure rate of only 3%, with no other changes?
Problem 6.41
A shaft is subjected to a maximum load of 10 kN. It is designed to withstand a load of 15 kN. If the maximum load encountered is normally distributed with a standard deviation of 2.5 kN, and if shaft strength is normally distributed with a standard deviation of 2.0 kN, what failure percentage would be expected?