The width of a slot of a duralumin forging is (in inches) normally distributed with µ = 0.9000 and ? = 0.0030. The specification limits were given as 0.9000 ±0.0050.
a) What percentage of forgings will be defective?
b) What is the maximum allowable value of ? that will permit no more than 1 in 100 defectives when the widths are normally distributed with µ = 0.9000 and ? (revised value)?