GIFSQ Tools · Module 1 — Food Composition & Proximate Analysis · Tool 15 of 500
Summarise replicate results: mean, sample standard deviation, range and relative standard deviation. Enter at least two replicates.
Try sample values — fills the form with the worked example below.
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Mean
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Sample SD
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RSD (%)
Equation: Mean = Σx ÷ n
Sample SD = √( Σ(x − mean)² ÷ (n − 1) )
Range = max − min · RSD % = SD ÷ mean × 100.
Method: Descriptive statistics for laboratory replicates, ISO 5725-2 (accuracy of measurement methods) — the sample SD divides by n−1; RSD is the coefficient of variation as a percentage.
Assumptions: the replicates are independent repeats of the same measurement, in the same units; the data are close enough to normal for a mean and SD to be a fair summary.
Limitations: with only two values the SD is rough; a single value has no SD at all; the SD describes spread, not bias against a true value.
Rounding: results to 2 decimal places, except the SD to 4 decimal places where the values are small; intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Sample SD = √( Σ(x − mean)² ÷ (n − 1) )
Range = max − min · RSD % = SD ÷ mean × 100.
Method: Descriptive statistics for laboratory replicates, ISO 5725-2 (accuracy of measurement methods) — the sample SD divides by n−1; RSD is the coefficient of variation as a percentage.
Assumptions: the replicates are independent repeats of the same measurement, in the same units; the data are close enough to normal for a mean and SD to be a fair summary.
Limitations: with only two values the SD is rough; a single value has no SD at all; the SD describes spread, not bias against a true value.
Rounding: results to 2 decimal places, except the SD to 4 decimal places where the values are small; intermediate values are not rounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Replicates 10.10, 10.30, 10.20. Mean = 30.60 ÷ 3 = 10.20. Deviations −0.10, +0.10, 0.00; sum of squares 0.02; SD = √(0.02 ÷ 2) = 0.10. Range = 10.30 − 10.10 = 0.20; RSD = 0.10 ÷ 10.20 × 100 = 0.98 %.
Enter values above to see results.
A standard deviation needs at least 2 values — with one replicate this tool reports an error, not a zero. As a guide, an RSD under 2 % is tight for most proximate work; check your own method limit. Tool 15 of 500 — GIFSQ
