Accuracy vs. Precision: The Similarities and Differences

Accuracy and precision are the terms used in scientific measurements but they are generally confused with each other. The main difference between accuracy and precision is that;

Accuracy is the extent to which the measurement readings are close or conform to the standard absolute value. On the other hand, precision is the exactness or reproducibility of the measurement readings, regardless of whether there is closeness to the absolute value or not.

Accuracy is the degree of closeness to standard value or being correct while, precision is the exactness or reproducibility of readings.

Accuracy vs Precision

Accuracy	Precision
Accuracy is defined as the extent to which the measured readings are close to the real or standard value	Precision is defined as the extent to which the measured readings are close to each other
It is the measurement of statistical bias	It is the the measure of statistical variability
It shows the degree of conformity	It shows the degree of reproducibility
Accuracy is dependent on precision i.e. very imprecise readings cannot be accurate	Precision is independent of accuracy i.e. readings can be inaccurate and still be precise
Inaccuracy comes from systematic errors e.g. instruments, apparatus, etc	Imprecision comes from random errors e.g. electronic noise, temperature, etc

What is Accuracy?

Accuracy is the measure of how close a value(s) is to the actual, standard, or true value. It is the measure of how closely a target is hit. In the personal win, scientific research, or any other case, accuracy is when you land directly on the main targeted value. if in case you are off the mark, the accuracy is termed low.

A single reading or event can be termed accurate and for many readings to be accurate, they have to be close to each other as well. That is why accuracy is dependent on precision for long-term accuracy.

Inaccurate readings persist due to systematic errors. It means that the non-accuracy of measurement is reproducible as long as the instrument or apparatus is not changed or corrected.

What is Precision?

Precision is the closeness of measured readings to each other, not the true value. Unlike accuracy, precision requires more than one reading to be established.

Precision is high when there is reproducibility in the measured readings and low if they are far off from each other. Precise measurement can be away from the true value and still be more correct. Imprecise readings are possible if there is an environmental condition that is continuously changing or something that alters every time a reading is noted.

Applications of Accuracy and Precision

There are several examples that help understand the concept of accuracy and precision. Let’s take an example from the physical world and one from the chemical world to see how accuracy and precision differ from each other.

Physical example(s)

1. For instance, let us take an example of an arrow shooting game. The archery target is made in concentric circles to see how close you were to the inner circle i.e. the main target.

If four arrows are shot and all four hit the inner circle somehow with small distances between them, the results are termed accurate and precise.
If the four arrows hit the inner circle but have significant spaces between them, the results are accurate and imprecise.
If the arrows do not hit the inner circle but still hit close to one another, the results are inaccurate but precise.
Similarly, if they hit at significantly different spots (not near one another or the target), the results are termed inaccurate and imprecise.

Chemical example(s)

2. In chemical systems, let’s take an example of a solution having a supposed concentration. Now the solution is run on concentration measuring techniques like; thin-layer chromatography (TLC) and uv-vis spectroscopy, etc. If the measured concentration is consistent with the supposed or original concentration, the results are called accurate. After repeated measurements, if the same results reproduce, the results are also precise.

Variations leading to different cases

Ideally, a measurement instrument is accurate and precise. It means that the measured values are close and clustered around the standard or true value. An instrument is established to be accurate or precise or both by the repeated measurements of some standard.

There are some cases in which a value can be accurate & precise, accurate & imprecise, inaccurate & precise, and inaccurate & imprecise. This variety of results depends upon the closeness to true value, exactness, and reproducibility of readings.

Accurate & Precise

If the measured readings in a scientific experiment or a condition are close to each other as well as close to the true value, the results are termed accurate and precise.

Accurate & imprecise

If the measured readings are close to the real value but they are not that close to each other, the results are termed accurate but imprecise.

Inaccurate & precise

Similarly, if the measured values are close to each other but they are distant from the true value, this condition is inaccurate but precise.

Inaccurate & imprecise

If in measured values, there is neither any closeness in between the values nor to the true value, the results are termed inaccurate and imprecise.

Key Takeaway(s)

Concepts Berg

When do accuracy and precision get confused?

Accuracy and precision being from the same scientific background, usually get confused because both mean ‘correct’, but in different ways.

Is accuracy better than precision?

Accuracy is better than precision when dealing with properly calibrated instruments, and fixed environmental conditions. However, for results to be accurate in the long run, they also have to be precise.

What is precise but, not accurate?

Some results or measurements that are close to each other but are not close to the real value, are precise but inaccurate.

What is an example of precision?

Closely placed readings in a scientific experiment are precise.

How can one be accurate but not precise?

One can be accurate but imprecise as his statements or results can be close to the real value but far away from one another.

How to describe accuracy and precision?

The best way to describe accuracy and precision is the dart board example. The results there can be accurate, precise, both, or none.

Would you rather be accurate or precise?

While dealing with instruments that are not properly calibrated, and not run against a standard, etc, I would be more precise than being accurate.
Similarly, while dealing with properly calibrated instruments and in such environmental conditions where physical parameters vary, I would be more accurate than being precise.

What is the difference between accuracy precision and reproducibility?

Accuracy is the correctness or closeness of a value to its true value. While precision is the reproducibility of results even if they are far from true values.

Is reproducibility accuracy or precision?

The property of reproducibility is termed precision.

Is percent error a measure of accuracy or precision?

Percentage error is generally more related to accuracy than precision.

Reference Book(s)

Biostatistics For Dummies By John Pezzullo, Ph.D. (Georgetown University Medical Center, Washington DC, USA)
Accuracy, Precision, and Analytical Measurements By DePauw University (Greencastle, Indiana)

Reference link(s)