What is statistical process control?

Statistical process control is a concept in personal epistemology: You cannot improve a workflow you do not measure. Track cycle time, throughput, error rate, and energy cost — but track them lightly, because invasive measurement distorts the very process you are trying to understand.

Example: You have a weekly reporting workflow that feels slow. You guess it takes about two hours. You start timing it — actually recording start and stop — and discover it takes three hours and forty minutes. Worse, you discover that ninety minutes of that time is spent hunting for data that should be pre-aggregated. Without measurement, you'd keep guessing the workflow was 'about two hours' and keep losing ninety minutes to a fixable bottleneck every single week.

This concept is part of Phase 41 (Workflow Design) in the How to Think curriculum, which builds the epistemic infrastructure for workflow design.