TS ISO 7870-4

TS ISO 7870-4 belongs to the control chart family and focuses on cumulative sum, or CUSUM, charts. It describes statistical procedures for establishing CUSUM schemes for process and quality control with both variables data and attribute data, and it sets out general decision-making methods for monitoring, control, and retrospective analysis using cumulative sum techniques.

What the CUSUM approach is designed to do

CUSUM charts track the accumulated effect of successive observations so that small but persistent departures from a target value become easier to detect. Where a conventional control chart tends to highlight sudden point-by-point shifts, CUSUM methods are often more sensitive to gradual drift and sustained process change. That makes them especially useful for identifying slow movement in process averages, creeping quality deterioration, or a stable-looking process that is consistently offset from its desired level.

Where this standard applies

• CUSUM schemes based on variables data
• CUSUM schemes based on attribute data
• Decision-making for monitoring and process control
• Retrospective analysis using CUSUM techniques

In general technical terms, CUSUM schemes help assess the time behaviour of a process mean, a defect rate, or another performance measure. Correct interpretation depends on consistent definitions of the reference value, direction of deviation, decision intervals, and alarm logic. TS ISO 7870-4 provides a statistical framework for that general approach; the detailed implementation depends on the process being monitored, the data type used, and the level of control sensitivity needed.