What is the Variation in Measurement System? | Types of Variation in Measurement System

Types of variation in Measurement System?

What is the Variation in Measurement System?

→ Variation is sometimes described as spread or dispersion to distinguish it from systematic trends or differences.
→ Measures of variation are either properties of a probability distribution or sample estimates of them.
→ The range of a sample is the difference between the largest and smallest value.
→ The observed variation in process output measurements is not simply the variation in the process itself, but it is the variation in the process plus the variation in the measurement that results from an inadequate measurement system.

Process Variation

Variation in a Measurement system:

→ The variation in the measurement system is mentioned in the below picture.

Variation in a Measurement system

→ Classification of Variation Related to Measurement System:
→ There are different sources of variation available in the measurement system.

➤ Types of observed process variation:

  1.  The actual process variation and 
  2.  The measurement variation.

     [1] The actual variation is due to the below parameter in the system
           e.g. Cycle time
                  Dimension data
                  Number of defects
                  Some other factor

     [2] The measurement variation further divided into two parts
          (A) Precision (related to variability)
          (B) Accuracy (related to a central location)

          (A) Precision is divided into 3 parts
                (a) Resolution
                (b) Repeatability
                (c) Reproducibility

          (B) Accuracy is divided into 3 parts
                (a) Linearity
                (b) Bias
                (c) Stability

→ Both have a common factor which is the variation within a sample.

➤ The classification of the observed variation is mentioned below:

 The observed variation is classified in a different category as mentioned in the below picture
Classification of variation