Understand Measurement Uncertainty for Better Decisions
All measurements involve a degree of uncertainty, but what does this actually mean? How does measurement uncertainty affect your decisions, and what can you do to improve the precision and accuracy of your measurement systems?
What is Measurement Uncertainty?
Measurement uncertainty is an expression of the doubt associated with a measurement result. It is often expressed as a symmetric interval around the measurement:
Measurement Result ± Measurement Uncertainty
Example: A measuring rod of 2000 mm ± 1 mm means that the actual length, with 95% confidence, lies between 1999 mm and 2001 mm.
Components of Measurement System Evaluation
A measurement system evaluation investigates two critical aspects:
- Precision: How consistent the measurements are:
- Repeatability: The ability to repeat the same measurement with the same instrument under identical conditions.
- Reproducibility: The ability to achieve consistent results with different operators or instruments.
- Accuracy: How close the measurements are to the actual value, including the evaluation of systematic errors.
Practical Experiences and Challenges
Our evaluations have uncovered several interesting findings:
- Experience vs. Authority: Operators who regularly perform measurements often achieve better precision than quality managers who rarely conduct tests.
- Technological Challenges: Camera controls provide high repeatability but require correct reference points to ensure accuracy.
- Subjective Assessments: When evaluating properties such as appearance or taste, we observe significant variability in reproducibility among individuals.
Consequences of Measurement Uncertainty
Lack of understanding of measurement uncertainty can lead to:
- Production errors and increased costs.
- Customer complaints and lost clients.
- Hidden systematic errors in the process.
Demonstration of Measurement Uncertainty
Sign up for our video demonstrating how weight measurements are affected by measurement uncertainty and the timing of measurements:
Learn to Evaluate Your Own Measurement Systems
Lean Tech offers courses in measurement system evaluation. We can also assess your measurement systems for you. Let us help you ensure reliable measurements for better decisions.