TS ISO 7873

TS ISO 7873 is a statistical process control standard focused on control charts for the arithmetic average, using warning limits and action limits. In piece and batch production, especially for large lots and mass output, monitoring a quality characteristic through sample averages helps reveal whether the process remains stable over time. This standard organises that approach into a consistent control-chart framework.

From a general technical standpoint, control charts are used to distinguish ordinary random variation from unusual variation by tracking how sample results change over time. An arithmetic-average chart works with subgroup means rather than individual readings, which makes shifts in the process level easier to detect. Warning limits provide an earlier signal layer before action limits are reached, supporting more graduated process monitoring.

How the limits support process decisions

The standard centres on plotting the sample arithmetic mean and using warning limits together with action limits for that purpose. Warning limits are early indicators that the process may be drifting away from its expected behaviour, while action limits represent a stronger alarm level. This distinction supports a stepwise decision model instead of relying on a single threshold.

What this document covers and where it applies

• It specifies procedures for statistical control based on charts of the sample arithmetic average.
• It is intended for large lots and mass production in piece and batch manufacturing.
• The measured quality characteristic is treated as a random variable with a normal distribution in the stated context.
• The abstract refers to cases where averages of four or more pieces are plotted on the chart.
• This TSE edition is catalogued as equivalent to ISO 7873:1993.