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Weighted mean count per g or mL from successive dilutions.
Note
N = ΣC / (V × (n₁ + 0.1 n₂) × d) = 422 / (1 × 2.2 × 10⁻²) = 1.9 × 10⁴ CFU per g or mL.
Reference: ISO 7218 general requirements for microbiological examinations of the food chain. Always follow your approved SOP and current pharmacopoeia.
N = ΣC / (V × (n₁ + 0.1 n₂) × d)
168 and 215 at 10⁻², 14 and 25 at 10⁻³, 1 mL → 1.9 × 10⁴ CFU/g
Use plates within the countable range of your method; report to two significant figures; low counts have their own rules in ISO 7218.