請問統計問題（ normal distribution ）
Calculate the probability of a defect and the expected number of defects for a 1000-unit production run in the following situations.
a.The process standard deviation is 0.15 ,and the process control is set at plus or minus one standard deviation. Units with weights less than 9.85 or greater than 10.15 ounces will be classified as defects.
b.Through process design improvements, the process standard deviation can be reduced to 0.05 . Assume the process control remains the same, with weights less than 9.85 or greater than 10.15 ounces will be classified as defects.
c.What is the advantage of reducing process variation and setting process control limits at a greater number of standard deviations form the mean?