MSA Example: Attribute or Categorical Data - Juran Institute

MSA for Attribute or Categorical DataBiasTrueValue orStandardBiasObservedAveragePossible Causes of Bias• Sensor not properlycalibrated• Improper use of sensor• Unclear procedures• Human limitationsMSA for Continuous Processes 4 .PPTAll Rights Reserved, Juran Institute, Inc.BiasBias is the difference between the observed average of measurements and the trueaverage. Validating accuracy is the process of quantifying the amount of bias in themeasurement process. Experience has shown that bias and linearity are typicallynot major sources of measurement error for continuous data, but they can be.In service and transaction applications, evaluating bias most often involves testingthe judgment of people carrying out the measurements.‣ExampleA team wants to establish the accuracy of its process to measure defects ininvoices. First, they gather a “standard” group of invoices and have an “expert”panel establish the type and number of defects in the group. Next, they have thestandard group of invoices measured by the “normal” measurement process.Differences between averages the measurement process came up with, and whatthe known defect level was from the expert panel represented the bias of themeasurement process.All Rights Reserved, Juran Institute, Inc.4#### XXXX.#### vx