Measurement system basics: bias, repeatability and gauge R&R

Skills you'll practise

• Distinguish resolution, bias, linearity, stability, repeatability and reproducibility, and give an example of each
• Calculate a gauge's bias from repeat readings of a reference part
• Set up and run a gauge R&R study fairly: representative parts, blind and randomized trials, the same method for every appraiser
• Read a gauge R&R summary (%Study Var, %Tolerance, number of distinct categories) and say which component dominates
• Choose the right next step when a gauge or an attribute check fails its study, and escalate within your authority

Course outline

1. 1.Measurement system basicsVideo · 2 min
2. 2.The measurement system, not just the gaugeLesson · 15 min
3. 3.Running a fair gauge R&R studyLesson · 15 min
4. 4.Reading results and acting on themLesson · 20 min
5. 5.Measurement system basics: bias, repeatability and gauge R&R: knowledge checkKnowledge check · 21 questions
6. 6.Measurement system basics: bias, repeatability and gauge R&R: practical exerciseKnowledge check · 1 question
7. 7.Final exam10 questions · passing it completes the course, so people who already know the material can test out

Sources it draws on

The lessons and questions are written from these references, so learners can go back to the original.

• NIST/SEMATECH e-Handbook of Statistical Methods: Gauge R&R studies (repeatability, reproducibility, stability, bias)
• NIST/SEMATECH e-Handbook: Gauge R&R studies, important issues (resolution, linearity, operator effects)
• NIST/SEMATECH e-Handbook: Bias and accuracy
• Minitab Support: Interpret the key results for Crossed Gage R&R Study (AIAG guideline: measurement variation under 10% of process variation is acceptable)
• Minitab Support: All statistics and graphs for Crossed Gage R&R Study (number of distinct categories; 5 or more acceptable per the AIAG MSA reference manual)
• Wikipedia: ANOVA gauge R&R (crossed 10 × 2 × 2 layout; precision-to-tolerance ratio below 0.1 and above 0.3)
• AIAG: Measurement Systems Analysis (MSA) reference manual (the automotive industry's MSA guidance; consult the current edition)
• Your site's quality manual, control plans, drawings, work instructions and procedures (these govern)