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Precision Formula:
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Precision, often expressed as Coefficient of Variation (CV), measures the reproducibility of test results. It quantifies the random error in laboratory measurements and is calculated as the standard deviation divided by the mean, multiplied by 100 to express as a percentage.
The calculator uses the precision formula:
Where:
Explanation: This calculation provides the Coefficient of Variation (CV), which is used in Westgard rules and quality control procedures to assess analytical precision.
Details: Precision calculation is essential for quality control in laboratory medicine. It helps determine the random error of analytical methods, establish quality control limits, and ensure test result consistency and reliability.
Tips: Enter the standard deviation and mean values from your quality control data. Both values must be positive numbers with mean greater than zero.
Q1: What is an acceptable CV value?
A: Acceptable CV varies by analyte and clinical context. Generally, CV < 5% is excellent, 5-10% is good, and >15% may require investigation.
Q2: How is precision different from accuracy?
A: Precision measures reproducibility (random error), while accuracy measures how close results are to the true value (systematic error).
Q3: What are Westgard rules used for?
A: Westgard rules are statistical quality control rules used to detect random and systematic errors in laboratory testing processes.
Q4: How often should precision be calculated?
A: Precision should be calculated regularly as part of routine quality control, typically with each new lot of reagents or monthly.
Q5: Can this calculator be used for all laboratory tests?
A: Yes, the precision calculation formula applies to all quantitative laboratory tests, though acceptable CV ranges vary by test type.