A shaft is subjected to a maximum load of 20 kN. It is designed to withstand a load of 25 kN. If the maximum load encountered is normally distributed with a standard deviation of 3.0 kN, and if shaft strength is normally distributed with a standard de viation of 2.0 kN, what failure percentage would be expected? Assume that the failure rate calculated 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 5%, with no other changes?
(b) To what value would nominal shaft strength have to be increased in order to give a failure rate of only 5%, with no other changes?