Shewhart Individuals Control Chart

Shewhart Individuals Control Chart

In statistical quality control, the individual/moving-range chart is a type of control chart used to monitor variables data from a business or industrial process for which it is impractical to use rational subgroups.

The chart is necessary in the following situations:

  1. Where automation allows inspection of each unit, so rational subgrouping has less benefit.
  2. Where production is slow so that waiting for enough samples to make a rational subgroup unacceptably delays monitoring
  3. For processes that produce homogeneous batches (e.g., chemical) where repeat measurements vary primarily because of measurement error

The "chart" actually consists of a pair of charts: one, the individuals chart, displays the individual measured values; the other, the moving range chart, displays the difference from one point to the next. As with other control charts, these two charts enable the user to monitor a process for shifts in the process that alter the mean or variance of the measured statistic.

Read more about Shewhart Individuals Control Chart:  Interpretation, Assumptions, Potential Pitfalls, See Also

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