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    "ISO 5725 duplicate-difference repeatability: s_r = √(Σ d_i² / (2m)) from m≥2 pairs. m=1 is rejected.",
    "d_i may be negative or zero. Both zero is valid (s_r = 0).",
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    "Not AIAG GRR EV = R̄/d2"
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      "title": "ISO 5725-1 — Accuracy (trueness and precision) of measurement methods and results",
      "section": "Repeatability standard deviation s_r",
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