Module 3 · Lesson 2 of 17
Operational definitions
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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
- Draft the definition with the process owner.
- Ask several inspectors to classify the same samples blind.
- Reconcile disagreements and edit the wording.
- Approve, publish and train before baseline data start.
Common mistakes
- Relying on photographs without decision rules.
- Changing definitions after baseline collection.
Knowledge check
Pick one answer per question. Explanations appear after you submit.
1. An operational definition must include:
2. Changing a definition mid-study is dangerous because:
Author: NOSK.life · Last reviewed: 2026-07-21