Let me say a few words about this, about the seven techniques of QC: generally speaking, it refers to the old seven techniques. Now the so-called new seven techniques have not been popularized in actual improvement and application. How to use skills mainly depends on whether it can help solve problems. Right? Seven techniques: look-up table method, hierarchical method, walking diagram, main factor diagram (fishbone diagram), histogram, Plato and control diagram: APQP, PPAP, MSA, FMEA and SPC. In fact, SPC is generally useful, and I personally think it is a little useful. . . The rest can't just take notes. Used in practical operation.