Difference Between Accuracy and Precision in Chemistry

The key difference between accuracy and precision in chemistry is that accuracy reflects how close a measurement to an accepted value (or a known value) whereas precision reflects how reproducible the measurements are.

Both the terms accuracy and precision gives the idea of how close a measurement is close to an actual value. But they are different from each other in definition and application. In chemistry, we use both these terms as analytical indicators for the values we get for certain experiments.

CONTENTS

1. Overview and Key Difference
2. What is Accuracy in Chemistry
3. What is Precision in Chemistry
4. Side by Side Comparison – Accuracy vs Precision in Chemistry in Tabular Form
5. Summary

What is Accuracy in Chemistry?

Accuracy in chemistry refers to how close a measurement to the true value. In order to increase the accuracy, we have to calibrate the instrument that we use to take the measurement. When calibrating, we should use a proper standard as the reference.

Figure 01: Precision vs. accuracy. (a) is neither precise nor accurate. (b) is precise and accurate. (c) is precise but inaccurate.

The accurate measurement should not have a systemic error or a random error. However, there are always errors occur when we take measurements from an analytical instrument, it can be either instrumental errors or human errors.

What is Precision in Chemistry?

Precision in chemistry is the reproducibility of a measurement. It is also a measure of how close the measurements are to each other. We use this terms, most of the times, for multiple measurements. This term describes how consistent the measurements are when we repeat the experiment. The repeated measurements reduce the random errors. The precision is independent of accuracy.

What is the Difference Between Accuracy and Precision in Chemistry?

Accuracy in chemistry refers to how close a measurement to the true value. In order to increase the accuracy, we have to calibrate the instrument that we use to take the measurement. Precision in chemistry is the reproducibility of a measurement. It gives the closeness of data in a dataset. Moreover, it is independent of accuracy.

Summary – Accuracy vs Precision in Chemistry

Accuracy and precision are independent of each other. The difference between accuracy and precision in chemistry is that accuracy reflects how close a measurement to an accepted value (or a known value) whereas precision reflects how reproducible the measurements are.

Reference:

1. Helmenstine, Anne Marie. “What Is Accuracy in Science?” ThoughtCo. Available here 
2. Helmenstine, Anne Marie. “Understand the Difference Between Accuracy and Precision.” ThoughtCo. Available here 

Image Courtesy:

1.’Precision versus accuracy’By CK-12 Foundation (raster); User:Adrignola (vector) – File:High School Chemistry.pdf, page 107, (Public Domain) via Commons Wikimedia 

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