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Uncertainty in Measurement: Accuracy and Precision

Uncertainty in Measurement: Accuracy and Precision

Scientists typically make repeated measurements of a quantity to ensure the quality of their findings and to evaluate both the precision and the accuracy of their results. Measurements are said to be precise if they yield very similar results when repeated in the same manner. A measurement is considered accurate if it yields a result that is very close to the true or the accepted value. Precise values agree with each other; accurate values agree with a true value.

Accuracy and Precision

Accuracy and Precision

Scientists typically make repeated measurements of a quantity to ensure the quality of their findings and to evaluate both the precision and the accuracy of their results. Measurements are said to be precise if they yield very similar results when repeated in the same manner. A measurement is considered accurate if it yields a result that is very close to the true or the accepted value. Precise values agree with each other; accurate values agree with a true value. Highly accurate measurements...

Units and Standards of Measurement

Units and Standards of Measurement

A physical quantity is defined either by specifying its measurement method or by stating how it is calculated from other measurements. For example, consider a metallic cube. We might define its mass and dimensions by specifying methods for measuring them, such as using a weighing machine and a meter scale. Then, we could define the volume by stating that it is the cube of its side, and we could calculate the density as the mass divided by the volume.
Measurements of physical quantities are...

Units and Standards of Measurement

Units and Standards of Measurement

A physical quantity is defined either by specifying its measurement method or by stating how it is calculated from other measurements. For example, consider a metallic cube. We might define its mass and dimensions by specifying methods for measuring them, such as using a weighing machine and a meter scale. Then, we could define the volume by stating that it is the cube of its side, and we could calculate the density as the mass divided by the volume.
Measurements of physical quantities are...

Uncertainty in Measurement: Reading Instruments

Uncertainty in Measurement: Reading Instruments

Counting is the type of measurement that is free from uncertainty, provided the number of objects being counted does not change during the process. Such measurements result in exact numbers. By counting the eggs in a carton, for instance, one can determine exactly how many eggs are there in the carton. Similarly, the numbers of defined quantities are also exact. For example, 1 foot is exactly 12 inches, 1 inch is exactly 2.54 centimeters, and 1 gram is exactly 0.001 kilograms. Quantities...

Random and Systematic Errors

Random and Systematic Errors

Scientists always try their best to record measurements with the utmost accuracy and precision. However, sometimes errors do occur. These errors can be random or systematic. Random errors are observed due to the inconsistency or fluctuation in the measurement process, or variations in the quantity itself that is being measured. Such errors fluctuate from being greater than or less than the true value in repeated measurements. Consider a scientist measuring the length of an earthworm using a...

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Related Experiment Video

Updated: Jul 13, 2026

Picometer-Precision Atomic Position Tracking through Electron Microscopy

Picometer-Precision Atomic Position Tracking through Electron Microscopy

Published on: July 3, 2021

Metrology in physics, chemistry, and biology: differing perceptions.

Venkatesh Iyengar¹

¹FSNSP, Tufts University, Boston, MA, USA. venkatesh.iyengar@tufts.edu

Biological Trace Element Research

|July 20, 2007

Summary

Chemical metrology, the science of measurement in chemistry, is evolving. While physics and basic chemistry rely on two measurement components, complex chemical analysis, especially in food samples, requires a third component: indirect measurements, impacting traceability.

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Area of Science:

Metrology
Physical Chemistry
Analytical Chemistry

Background:

Metrology in physics relies on two components: the measure (unit) and the measurand (entity measured).
Physical and analytical chemistry traditionally apply these metrological principles using measures like molar relationships and techniques such as gravimetry.
Basic metrology ensures measurement integrity through well-defined units and measurands.

Discussion:

Extending metrology to complex chemical matrices, like food samples, introduces a third component: indirect measurements.
Techniques such as Atomic Absorption Spectroscopy (AAS) for determining zinc in foods exemplify this addition.
This transition necessitates additional steps to ensure the traceability and reliability of chemical measurements.

Key Insights:

Chemical metrology differs from physics metrology when dealing with complex matrices.
Indirect measurements are crucial for field assays in chemical analysis.
Traceability in chemical metrology is becoming more complex.

Outlook:

The field of chemical metrology is continuously evolving.
Further development is needed to address the complexities of indirect measurements and traceability in chemical analysis.
Ensuring the reliability of measurements in complex chemical systems remains a key focus.