GIFSQ Tools · Module 14 — LIMS & Quality · Tool 267 of 500
Review three replicate results: mean, sample standard deviation, relative standard deviation and the range — then check the mean against the specification.
Try sample values — fills the form with the worked example below.
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Mean
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Standard deviation
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RSD (%)
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Range
Equation: Mean = (r1 + r2 + r3) ÷ 3. Sample standard deviation s = √[Σ(ri − mean)² ÷ (3 − 1)]. RSD (%) = s ÷ mean × 100. Range = highest − lowest replicate. The mean passes when it lies inside the specification limits, endpoints included.
Method: Replicate review per ISO/IEC 17025:2017, clause 7.7 (ensuring the validity of results) and ISO 5725-2 (repeatability standard deviation, n − 1 denominator). The specification limits come from the product specification, not from this tool.
Assumptions: the three replicates are independent determinations of the same sample under repeatability conditions.
Limitations: three replicates give only a rough spread — a wide RSD with three values may still be chance, and a tight RSD does not prove the result is unbiased.
Rounding: mean, standard deviation and range to 2 decimal places; RSD to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value. Records are kept only in this browser on this device (localStorage); this is a device-only record aid, not a shared multi-user LIMS, and nothing is sent to any server.
Method: Replicate review per ISO/IEC 17025:2017, clause 7.7 (ensuring the validity of results) and ISO 5725-2 (repeatability standard deviation, n − 1 denominator). The specification limits come from the product specification, not from this tool.
Assumptions: the three replicates are independent determinations of the same sample under repeatability conditions.
Limitations: three replicates give only a rough spread — a wide RSD with three values may still be chance, and a tight RSD does not prove the result is unbiased.
Rounding: mean, standard deviation and range to 2 decimal places; RSD to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value. Records are kept only in this browser on this device (localStorage); this is a device-only record aid, not a shared multi-user LIMS, and nothing is sent to any server.
Worked example: Replicates 10.1, 10.3 and 10.2 against 9.5–10.5: mean 10.20, standard deviation 0.10, RSD 0.98%, range 0.20 — the mean passes.
Enter values above to see results.
A result outside the specification goes to the out-of-specification workflow (Tool 271), not to a quiet retest. Tool 267 of 500 — GIFSQ
