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Mean / SD / CV Calculator

Free Statistical Calculator for Laboratory Quality Control

Your measurements

Use a period (.) for decimals. Separate values with a new line, a space, or a comma followed by a space (e.g. 12.3, 12.4).

Tabs and semicolons are also accepted. Enter 2–10,000 measurements. Do not enter patient-identifiable information.

Units label your results; they do not convert the measurements.

Your results

Enter at least two measurements to begin.

Measurements
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Mean
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Sample SD (n − 1)
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CV (%)
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Sample SD uses n − 1. Some analysers or statistical software use population SD (n), which may produce different results.

CV is N/A when the mean is zero or negative. Calculations use unrounded values; very small values may use scientific notation.

Reading the statistics

Mean: where results are centred

The arithmetic mean is the sum of the measurements divided by n. It describes their centre, but does not describe their precision by itself.

Sample SD: how widely results vary

Sample SD = √[Σ(xᵢ − Mean)² / (n − 1)]. It describes spread around the mean in the same unit as the measurements.

CV: variation relative to the mean

CV (%) = Sample SD / Mean × 100. CV describes relative variation at a positive mean. A low CV does not automatically establish acceptable analytical performance; interpretation depends on measurement level, method and intended use.

Learn how Mean, SD and CV are calculated → QC Article 02

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Measurements are processed locally in your browser. HemeLabNotes does not upload or store the values entered into this calculator.

Educational disclaimer

This calculator is intended for educational and analytical support. The calculated statistics do not establish validated QC targets, acceptance limits or analytical suitability. Laboratory decisions must follow established procedures, applicable quality standards and clinical requirements.