seven points trending

**Seven Points Trending** is an SPC (Statistical Process Control) rule detecting systematic process drift when seven or more consecutive points show a consistent upward or downward trend. ## What Is the Seven Points Trending Rule? - **Trigger**: 7+ consecutive points each higher (or lower) than previous - **Signal**: Process shift in progress, not random variation - **Action**: Investigate before out-of-control condition develops - **Rule Origin**: Western Electric / Nelson rules for control charts ## Why Seven Points Trending Matters Random variation rarely produces seven consecutive moves in one direction (probability <1%). This pattern indicates assignable cause requiring intervention. ```svg Control Chart with Trending Pattern:UCL ───────────────────────────────── ● ● ● ● ← 7-point upward trend ● ●CL ───────────●────────────────────── ●LCL ───────────────────────────────── 1 2 3 4 5 6 7 8 9 10 11Points 3-9: Each higher than previous → Trigger rule ``` **Common Causes of Trending**: - Tool wear (gradual degradation) - Chemical depletion - Temperature drift - Operator fatigue across shift

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