Operational definitions

Learning objectives

• Write operational definitions that remove classification ambiguity.
• Include instrument, method, unit, conditions and decision rule.
• Distinguish conceptual meaning from operational meaning.

What a definition must contain

• Unit, opportunity, defect and sampling point.
• Instrument, resolution and calibration status.
• Method, conditions, rounding and exclusions.
• Explicit acceptance/rejection decision rule.

Garment-factory example

‘Open seam’ becomes: a visible separation where stitches fail to join the specified plies, observed after sewing and before repair, counted once per location using the approved defect reference card under 1000-lux inspection light.

Method

1. Draft the definition with the process owner.
2. Ask several inspectors to classify the same samples blind.
3. Reconcile disagreements and edit the wording.
4. Approve, publish and train before baseline data start.

Common mistakes

• Relying on photographs without decision rules.
• Changing definitions after baseline collection.