Replying to
@daisy
Eduard Demming, the cannonical author of stats and process control, had some maxims... one of which was,
"it costs far more to rework a defective product than it does to make it in the first place."
When there is a process in place that's tuned to reliability, every piece is more of the same. Every defective piece is unique.
If the raw material is defective, fixing a defective product is chasing randomness, so buy better spec'd raw material. or refine the process.