Hi, Let's be specific about false alarm% and %missed . False alarm suggests that the object is actually good but alarm is showing as bad object. This might cause inhouse rejection increase but customer is not bothered about it. Missed rate suggests that the object is actually not good (NG) but passed. This action will pass the NG object to customer and based on the severe nature of the NG , a customer complaint may arise. So, missed rate should be treated more seriously. Statistically for attribute measurement < 2% missed rate is considered as good and < 5% false alarm are considered in good catagory as general guideline. Regards, Sourav Das Six Sigma Professional