Beginner Topic 882 of 1102 Analytical, Lab & Spectroscopy
Accuracy and Precision
Accuracy is closeness to the true value; precision is reproducibility of results.
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In-depth explanation of Accuracy and Precision
Accuracy describes how close a measured value is to the true or accepted value, and it is degraded mainly by systematic errors such as an uncalibrated instrument or a biased method. Precision describes how closely repeated measurements agree with one another, and it is governed by random errors that scatter results unpredictably. A measurement set can be precise but inaccurate, which happens when a consistent bias shifts every result in the same direction. Good analytical work requires both, and precision is quantified by the standard deviation or relative standard deviation of replicate results. Calibration against certified reference materials is the main way to detect and correct accuracy problems.
Going deeper: Accuracy and Precision
Key ideas: Quantify accuracy as percent error = (measured minus true)/true x 100, and precision as standard deviation or percent RSD of replicates. A tight cluster away from the true value signals a systematic error such as zero-offset or contaminated reagent. Scattered values around the true mean signal random error. Calibrate with a certified reference material and run replicates to see both.
Common mistakes and connections: The most common mistake is treating the two words as synonyms. Another is believing that more replicates cure a systematic error, when averaging only reduces random scatter. A digital readout with many digits can look precise yet be inaccurate. Links to error analysis, standard deviation, calibration and quality control.
Visualization of Accuracy and Precision
Two replicate distributions centred on the true value 10: a narrow one is precise, a wide one is imprecise. A narrow peak shifted away from the true value would be precise but inaccurate. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A balance that reads 0.02 g high every time gives precise but inaccurate masses.
Frequently asked questions about Accuracy and Precision
What is Accuracy and Precision?
Accuracy is closeness to the true value; precision is reproducibility of results.
Is Accuracy and Precision a beginner, intermediate or advanced topic?
Accuracy and Precision is a beginner topic in Analytical, Lab & Spectroscopy. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Accuracy and Precision?
Study these earlier topics in Analytical, Lab & Spectroscopy first: Chemical Hazard Symbols, Measurement and Units, Significant Figures.
What comes after Accuracy and Precision?
The next topics in Analytical, Lab & Spectroscopy are Scientific Notation and Dimensional Analysis.
Can I practise Accuracy and Precision with quizzes?
Yes. The interactive lesson includes a self-check question on Accuracy and Precision, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Accuracy and Precision fits in Analytical, Lab & Spectroscopy
Accuracy and Precision is topic 6 of 99 in Analytical, Lab & Spectroscopy.