Please contact Media Sciences if your questions are not answered on these pages. Unfortunately, no one clearly defines what a defect is. Instead, some irrelevant spec like BLER or clip may be referenced. High quality media should meet dozens of electrical, visual, and mechanical criteria. When statistical methods are used to analyze natural variations in performance, they predict that manufacturers should be capable of supplying media with less than 100 parts per million defects.
Unnatural events can increase natural reject rates by ten or even one hundred times.
Such events may occur when the user tests media. Poor test methods or unrealistic specifications can produce false results. Abnormal events during manufacture can also increase rejects. Management decisions to use nonconforming material or mistakes by an untrained or overworked operator are two examples. Another unnatural event is the use of duplication yield to evaluate media quality.