Difference between Accuracy and Precision

Precision refers to the closeness of multiple reading of the same quantity, whereas accuracy refers to the measured value to the true value. In this article we will discuss difference between accuracy and precision.

Accuracy and Precision are two ways to measure results. Both are useful ways to track and report on project results. Precision is defined as the level of variation that lies in the level of several measurements of the same factor. In contrast, accuracy is the level of agreement between actual and absolute measurements. This article will discuss the difference between accuracy and precision.

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Table of Content

• Precision vs. Accuracy
• What is Precision?
• What is Accuracy?
• Example
• Key Difference between Precision and Accuracy

Precision vs. Accuracy

Parameter	Precision	Accuracy
Definition	Refers to the closeness of multiple readings of the same quantity.	Refers to the nearness of the measured value to the true value.
Measurement Method	Multiple factors are used for measurement.	One factor used for measurement.
Mutual Relationsip	Item may or may not be accurate.	Items have to be precise in most classes.
Dependency	Precision is not dependent on accuracy.	Accuracy is not dependent on precision.
Degree	Degree of Reproducibility	Degree of Conformity
Error	Random Error	Systematic Error

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What is Precision?

Precision is a measurement of exactness, which refers to how close two or more measurements are to each other.

• It represents uniformity or repeatability in the measurement.
• Measures the extent to which the result is close to each other.
• Variations between the measurement are less if the level of precision is very high.
• It is possible for precision that measurements are not to be accurate.
• Precision can be of two types:
  • Repeatability
    • It is a precision measurement variation that is done under the same condition
    • Measurements are taken frequently over a short period of time
  • Reproducibility
    • Opposite to Repeatability
    • The process is done over a long period of time.
    • Here, variations arise when the same process is used over the different instruments.

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What is Accuracy?

Accuracy refers to the degree to which the result of a measurement is close to the standard value.

• i.e., to which extent the actual measurement is close to the standard value.
  • The closer the measurement, the higher will be the accuracy.
• Accuracy can be of three types:
  • Point Accuracy
    • Refers to the accuracy of an instrument at one particular point on its scale.
    • It is not equal (or same) to the general accuracy.
  • Percentage Accuracy
    • It is obtained by multiplying the accuracy percentage by the pressure reading.
    • Accuracy will be higher if the pressure measurement is less.
  • Accuracy as a percentage of True Value
    • Derived by calculating true value by its true value.

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Example

Let’s take an example of pistol shooting. In pistol shooting, players try to hit the bull’s eye ( i.e., the target’s center) to score more in multiple rounds.

• High Accuracy and Low Precision – when the bullets hit the target at a different point but close to the bull’s eye.
• High Accuracy and High Precision – when all the bullets hit the bull’s eye.
• Low Accuracy and Low Precision – when the bullets hit the target at different points away from the bull’s eye.
• Low Accuracy and High Precision – when all the bullets hit the same target repeatedly but not the bull’s eye.

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Key differences

• Precision is defined as the level of variation that lies in the level of several measurements of the same factor. In contrast, accuracy is the level of agreement between actual and absolute measurements.
• Accuracy is the degree of closeness to the true value, whereas precision is the degree to which a process would repeat the same value.
• Precision is a measure of statistical variability, whereas accuracy measures statistical bias.
• Precision is concerned with random errors, whereas accuracy focuses on systematic errors.

Conclusion

In this article, we have briefly discussed precision and accuracy their differences and examples.

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