Quality Assurance Line: Rolled Throughput Yield

Inspection Stations

Line Controls

Incoming defect rate 4.0%

Spawn rate 2.0 units/s

Live Metrics

Rolled Throughput Yield

0.0%

Estimated DPMO

Units shipped good

Units scrapped

How it works

Every unit enters the line with a chance of carrying a hidden defect, set by the incoming defect rate. It then passes through a series of inspection stations. Each station has an inspection effectiveness p_i — the probability it correctly detects a defective unit. A detected defect is sent to rework (fixed and re-tested at the same station); an undetected defect silently escapes to the next station, and a defect that escapes every station ships as a hidden failure.

Station yield:  Y_i = fraction of units leaving station i defect-free
Rolled Throughput Yield: RTY = Y_1 × Y_2 × ... × Y_n
DPMO ≈ (1 − RTY) × 1,000,000

RTY is the classic Six-Sigma-adjacent metric for a multi-stage process: it is always lower than any single station's yield, because defects that slip past an earlier, weak station compound with the ones introduced or missed later — this is the "hidden factory" effect. Raising a station's slider increases the fraction of true defects it catches (true positive rate) at that stage, directly raising the line's overall RTY. Apply Corrective Action models a root-cause fix: it permanently lowers the incoming defect rate a little, simulating an upstream process improvement rather than just catching more defects downstream.

Station sliders — set each station's detection probability (its inspection rigor).
Incoming defect rate — the raw defect probability of a freshly spawned unit, before any inspection.
Corrective action — a real quality-improvement lever: reduces defects at the source instead of catching more downstream.

Good unit Defective (undetected) Caught → rework

Throughput 0/s

Units in line 0

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