1. The problem statement, all variables and given/known data Plastic rods are cut into nominal length of 6 inches. Actual lengths are normally distributed about a mean of 6 inches and their standard deviation is 0.06 inch. Question: To what value does the standard deviation need to be reduced if 99% of the rods must be within tolerance? 2. Relevant equations sd=standard deviation u=mean P(a<X<=b)=F((b-u)/(sd))-F((a-u)/(sd)) 3. The attempt at a solution since they want the possibility of rods to be between u+sd and u-sd to be 0.99, b=u+sd and a=u-sd and the equation will become P(a<X<=b)=F((u+sd-u)/(sd))-F((u-sd-u)/(sd)) F(1)-F(-1) doesn't equal to 0.99. Am I misinterpreting the word tolerance? I dont know what else to try... please help thank you!