Difference between accuracy and precision
by Yogi P - November 5, 2023
Difference between accuracy and precision | Accuracy vs Precision
In various fields, from science and engineering to everyday language, the terms ‘accuracy’ and ‘precision’ frequently crop up. Though they may sound synonymous, and are often used interchangeably, they have distinct definitions and implications, particularly when it comes to measurement and data quality.
This article aims to explain the differences between accuracy and precision in detail.
Understanding Accuracy
Accuracy refers to the closeness of a measured value to a standard or known value. It’s an indicator of correctness – how close a measurement is to the actual true value.
Understanding Precision
Precision, contrasts with accuracy, describes the closeness of two or more measurements to each other, regardless of whether those measurements are accurate. It indicates consistency or repeatability.
The Target Analogy
Imagine a target with a bullseye representing the true value. Accuracy is akin to how close the arrows hit to the bullseye, while Precision is how close the arrows are to each other, even if they’re not hitting the bullseye.
Accuracy in Detail
Accuracy captures the quality of a single measurement. It’s a measure of validity and correctness. For instance, if a clock strikes twelve when it’s actually noon, it’s accurate.
Characteristics of Accuracy:
- Reflects the true value.
- Is independent of precision.
- Can be improved by calibration and eliminating systematic errors.
Precision in Detail
Precision is about the quality of a group of measurements. If you weigh a bag of flour five times and get nearly the same reading each time, your scale is precise.
Characteristics of Precision:
- Reflects the reproducibility of measurements.
- Does not require a known standard for comparison.
- Can be affected by random errors, but not corrected by calibration.
Measuring Accuracy and Precision
Instruments and Methods:
- To measure accuracy, you compare against a standard or known value.
- To assess precision, you compare the set of measurements against each other.
Examples in Practice
Accuracy Example: A medical thermometer that reads 98.6°F when the actual body temperature is 98.6°F is accurate.
Precision Example: If that same thermometer gives readings of 98.6°F, 98.7°F, and 98.6°F on three consecutive measures, it is precise.
Misconceptions and Common Errors
A common error is assuming that a precise instrument is also accurate, or vice versa. An instrument can be one without the other: for example, a scale consistently giving wrong readings is precise but not accurate.
Overview Table: Accuracy vs. Precision
| Aspect | Accuracy | Precision |
|---|---|---|
| Definition | Closeness to the true value. | Closeness of repeated measurements to each other. |
| Indicator | Correctness and validity. | Consistency and repeatability. |
| Measurement | Comparison against a standard or known value. | Comparison among the set of measurements. |
| Dependence | Dependent on the correctness of the system. | Independent of accuracy, but not of the system. |
| Improvement | Calibration and eliminating systematic errors. | Refinement of technique and reducing random errors. |
| Error Type | Systematic errors affect accuracy. | Random errors affect precision. |
| Example | A clock that strikes twelve at noon is accurate. | A clock that strikes twelve at the same time every day is precise. |
| Visual Analogy | Arrows hitting the bullseye. | Arrows grouped closely together, whether near the bullseye or not. |
| Requirement | Requires a known standard for comparison. | Does not need a standard for comparison. |
| Industry Example | A lab test correctly identifying a disease is accurate. | A lab test consistently producing the same results is precise. |
Impact in Various Fields
In fields like manufacturing, healthcare, and research, both accuracy and precision are paramount. An inaccurate tool can lead to faulty products, misdiagnoses, or erroneous data, while imprecision can result in lack of confidence in repeated measurements or outcomes.
Achieving Both Accuracy and Precision
To achieve both, one must calibrate instruments properly, ensure quality control, and refine measurement techniques to reduce errors.
Educational Importance
Understanding the difference between accuracy and precision is essential in education, especially in STEM fields where students must learn to measure and interpret data correctly.
Tips for Remembering the Difference
To remember the difference, think of accuracy as ‘hitting the target’ and precision as ‘consistency’, regardless of whether the target is hit.
Conclusion
In conclusion, while both accuracy and precision are crucial to the integrity of measurement, they serve different roles. Accuracy is about hitting the bullseye – measuring what you intend to measure. Precision is about how consistently you can hit the same spot – repeating your measures reliably.
An understanding of both concepts is vital for professionals across various industries, for whom the quality of measurement can be the difference between success and failure.
In the practical world, a balance of accuracy and precision is often required to ensure the reliability and credibility of any work involving measurements. Whether you’re a scientist conducting experiments, a manufacturer producing parts, or a student in a lab, grasping these concepts and applying them can elevate the quality of your work and the conclusions you draw from it.
