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Measurement System Analysis (MSA)

Will Six Sigma Be Relevant For The Future
  • MSA determines the amount of variation due the measurement system. The objective method is to assess the validity of a measurement system and minimize the variation due to Measurement.
  • Measurement Systems Analysis (MSA) is a tool for analyzing the variation present in each type of inspection,measurement, and test equipment.
  • MeasurementVariation can be classified as below
Will Six Sigma Be Relevant For The Future

Discrimination

Will Six Sigma Be Relevant For The Future
  • If the red distributions illustrate the process variation, we would not be able to detect small (decimal) changes to the process using the first measurementinstrument.
  • The second measurement device has better discriminationthan the first.

Accuracy

Will Six Sigma Be Relevant For The Future
  • Accuracy is how close a value is to its true value. An example is how close an arrow gets to the dartboard center.
  • Accuracy is how close a value is to its true value. An example is how close an arrow gets to the dartboard center.
Will Six Sigma Be Relevant For The Future

Precision

Will Six Sigma Be Relevant For The Future
  • Precision is how repeatable a measurement is. An example is how close a second arrow is to the first one
  • Precision describes the variation you see when you measure the same part repeatedly with the same device. It includes two types of variation Repeatability & Reproducibility

Accurate & Precise

Will Six Sigma Be Relevant For The Future
  • The Measurement system must be both Accurate & Precise

Precision

Will Six Sigma Be Relevant For The Future
  • Repeatability: The variation due to Measurement Gauge or poor gauge design. It is often the result of poor design ofthe gauge or gauge system
  • Repeatability for Measurement System can be found out by repeated measurement of the same unit with Same Location, Same Measuring tools, Same Operator, Same Parts.
  • From the image below:
    - Variation by Gauge A is lesser than B or
    - Repeatability will be better with Gauge A
  • Reproducibility: The variation contributed due to Appraisers (measuring people)
  • Reproducibility for Measurement System can be found out by repeated measurement of different units with below conditions*
  • Same Location, Same Measuring tools, Different Operators, Different Parts
  • Note: *Conditions are industry-specific. Given conditions are for Manufacturing & Service industry only, NonResearch oriented, Non-Pharma or Bio
  • The variation in average measurements between Operator B and C is much less than the variation between Operators A and C. Therefore, the gage's reproducibility is too low.
Will Six Sigma Be Relevant For The Future

Measurement Stability

Will Six Sigma Be Relevant For The Future
  • Measurement stability is the measurement system's capacity to produce the same values over a given time range while measuringthe same sample.
  • Master component or controlled component is measured over time, and the Bias is calculated and plotted against the time using control charts. Measurement is stable, meaning the absence of a special cause leaving only the common cause.
  • Let us consider the below data where Master gauge measurementis taken for 10 days and Bias is calculated
  • Inference: As the Bias values are within the control limit and no special cause noticed, we can conclude that Bias in control and Measurementis Stable
Will Six Sigma Be Relevant For The Future

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