The alert
The first message arrives before the supplier is late
These two alerts are the product. The first one fires on the spread. The second one fires on the mean, four days later, and by then a scorecard would have caught it too. The gap between them is the part you can act inside.
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Lead TimeAPP#eng-alerts🔴 Lead-time variance jumped +153%supplier=Kestrel Machining
Baseline
4.343
Now
11.001
Confidence
99.9%
Started
Aug 9
Supplier
Kestrel Machining
Promised
18 days
Variance flagged
Aug 9
Mean flagged
Aug 13
Likely cause · Lead-time variance on Kestrel Machining broke first, flagged Aug 9, while mean lead time was still inside its normal range. The mean followed on Aug 13, defect rate roughly tripled, and on-time delivery fell about twenty percent. The four-day gap is the usable part: a supplier under strain becomes inconsistent before it becomes late, so the spread is the earlier signal. Nothing moved on the other three suppliers, and the all-supplier on-time rate never left its band because this supplier is a small share of order lines.
- 1.Call Kestrel before the next release: ask what changed on the line in the week to Aug 9.
- 2.Re-plan safety stock on Kestrel parts against the new lead-time distribution, not the promised 18 days.
- 3.Pull incoming inspection records for Kestrel lots received after Aug 13.
AcknowledgeFalse positiveCUSUM · q < 0.0001 · BH-corrected
L
Lead TimeAPP#eng-alerts🔴 Actual lead time jumped +45.7%supplier=Kestrel Machining
Baseline
18.513
Now
26.968
Confidence
99.9%
Started
Aug 13
Supplier
Kestrel Machining
Promised
18 days
Variance flagged
Aug 9
Mean flagged
Aug 13
Likely cause · Lead-time variance on Kestrel Machining broke first, flagged Aug 9, while mean lead time was still inside its normal range. The mean followed on Aug 13, defect rate roughly tripled, and on-time delivery fell about twenty percent. The four-day gap is the usable part: a supplier under strain becomes inconsistent before it becomes late, so the spread is the earlier signal. Nothing moved on the other three suppliers, and the all-supplier on-time rate never left its band because this supplier is a small share of order lines.
- 1.Call Kestrel before the next release: ask what changed on the line in the week to Aug 9.
- 2.Re-plan safety stock on Kestrel parts against the new lead-time distribution, not the promised 18 days.
- 3.Pull incoming inspection records for Kestrel lots received after Aug 13.
AcknowledgeFalse positiveCUSUM · q < 0.0001 · BH-corrected
Why the order matters
Every supplier scorecard in this category averages. Averaging is the operation that destroys the earlier of these two signals, because a distribution can widen a long way before its mean moves at all. Treating dispersion as its own series, with its own detector, is the only reason the first message exists.