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?
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
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!