Statistical quality control and gas lamp: what they have in common

1. Step 1. Statistical quality control — uses — Statistics. Statistics.
2. Step 2. Statistics — uses — Hollerith tabulator. Processing censuses.
3. Step 3. Hollerith tabulator — has part — Relay. Relays controlled the sorting box.
4. Step 4. Relay — is part of — Traffic light. Relay controllers.
5. Step 5. Traffic light — uses — Coal gas. A gas lamp lit the signal.
6. Step 6. Coal gas — is used in — Gas lamp. Coal gas.

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