TS ISO 7870-4

TS ISO 7870-4 is the part of the ISO 7870 series that addresses statistical procedures for cumulative sum (CUSUM) control charts used in process and quality control. It defines general decision-making methods for monitoring, control, and retrospective analysis using cumulative sum techniques for both variables data and attribute data.

What cumulative sum schemes are designed to do

A CUSUM approach is a control-chart technique intended to reveal small, persistent shifts in process performance earlier than many point-by-point charts. Instead of looking only at each sample in isolation, it accumulates deviations from a target over time, making departures from the desired level easier to detect. In general technical terms, this makes CUSUM especially useful where process stability, gradual drift, and early warning are important in manufacturing and other quality-focused operations.

Data types covered in this part

• Variables data: measured numerical data obtained from quantitative observations.
• Attribute data: classified observations such as conformance, defect counts, or similar discrete results.
• Monitoring and control: decision-making for tracking the current state of a process.
• Retrospective analysis: evaluating past data to understand process behaviour.

This standard focuses on the statistical procedures for setting up CUSUM schemes, so it provides the framework and logic of use rather than a single fixed application scenario. In broader technical context, such schemes are associated with target values, shift magnitude, and decision limits, and they occupy a distinctive place within the family of control charts. Read together with statistical terminology standards such as ISO 3534-1 and ISO 3534-2, it supports a consistent language for interpretation and use.