No amount of checking or inspection for defects will reveal what is going on in a defective process, or indicate the capacity of the process for improvement. In almost every case checking or inspection is too late, very costly and, above all, cannot add one iota of quality to a product. Deming's analogy of "scraping burnt toast" is the best metaphor for our detection (inspection or checking) method of production. Everything that has to be corrected or done over is waste, costs doubt on the acceptability of the materials that passed "quality control.