Examples

When Trends Matter and When They Do Not | Surface Finishing Software

When Trends Matter and When They Do Not

A meaningful process trend is directional movement in manufacturing process data that exceeds what random variation would produce under stable process behavior. Not every trend is actionable: most directional runs are statistical noise, not a real change in the process. Statistical process control (SPC) distinguishes the two by comparing the pattern against probability-based thresholds, typically six consecutive points in one direction, and interpreting that pattern with operational context before anyone adjusts the process.

Why Control Limits Don't Detect Gradual Process Drift | Lab Wizard

Why Control Limits Don’t Detect Gradual Process Drift

A nickel bath runs for six months. Every daily titration falls within control limits. Then a customer sends back parts with adhesion failures. The investigation finds bath chemistry shifted 8% from its original target. Every measurement was in control. Nothing on the chart was wrong, and nothing was wrong with SPC either.

Noise vs Actionable Change in Plating Processes | Lab Wizard

Noise vs Actionable Change in Plating Processes

A nickel plating run finishes and the thickness readings show a slight shift from the previous batch. The operator adjusts the rectifier current. The next batch shifts back the other way. Another adjustment. Three runs later, the process is more variable than it was before anyone touched anything.