Accuracy & Precision: What is the Difference?

This image describes accuracy and precision

Accuracy and precision are two important things in measurement. Both of them determine how reliable and trusted a certain instrument is. As someone who will be using a measuring instrument, it may be difficult to differentiate them. Here, we have a good chance to break it down altogether.

Accuracy

It means how close the measurement to the real/true/agreed result. The easiest way to describe accuracy is archery. When the arrow hits the center of the target, it means it hits very accurately. If it hits near the center, it means accurate. Moreover, if it hits far from the center, it’s less accurate or even no accurate at all.

Another example that can explain it is by a length measure. As we know that 1 meter is declared as the length of light traveling in a vacuum area for 1 / 299 792 458 of a second, any 1-meter ruler that is close to that light length in vacuum associates to accuracy. It is close to the true/agreed result.

The state of accuracy is determined by how close. That being said, the less difference your ruler to the agreed 1-meter standard length measure, the more accurate your ruler. It doesn’t matter if your ruler is more or less in length, as long as it’s near to the true value, it means accurate.

Precision

It means how consistent the measurement to the initial result even though it happens repeatedly. You measure an object’s temperature and find it 30°C. Secondly, you measure it again and notice it 29°C. Thirdly, you repeat it, it’s 31°C. And the last one is 29,5°C. Even though the actual temperature is 40°C, the consistency shows precision there because the next to the last results remain stable to the starting one.

Precision also has another meaning. When you have a tape measure and find your tape uses imperial/US unit, you might find the smallest scale is 1/8 inch, you measure a particular length and the result 10 inches, then the precision of your measurement is 10 ± 1/8 inches. In other words, it means the tolerated error of your measurement or the range area of measurement. So, the object’s length locates between 9 7/8 inches to 10 1/8 inches.

Accurate and Precise

A powerful, reliable, and trusted measuring instrument should provide accuracy and precision. It matters especially when it’s needed to measure a crucial measurement. The image above could represent how accuracy and precision are combined and results in a nice score.

Accurate and precise measurement should occur in every aspect of measuring including while using a tape measure. As long as the tape manufactured as accurately as possible nearest to the standard, then completed by having 1/16 precision/increment, it suffices to serve better measurement.

A good measuring instrument must have both accuracy and precision. Both of them are about the quality of the measurement. We have to understand the difference between them. Accuracy is about close to the real value, while precision is about close to the first value no matter it’s near or far from the real value.

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