Accuracy vs Precision : What is the difference

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Accuracy and precision are two terms that we encounter in our daily life. No matter we are a sportsperson, engineer or doctor. Accuracy and precision plays a very important role in our day to day repeated tasks. But these two terms always confuses us. In this article we will try to understand the difference between these two : Accuracy vs Precision. 

Accuracy and precision are used to evaluate the performance of a repetitive task. They also reflect the extent of the deviation from actual value. For example When a sports person shoots a bull’s eye. If every time he hits the center, he is accurate.

If every time sports person hits in the last circle. But all hits are at the same point. He is still precise but not accurate.

Accuracy

Accuracy is how close a measured value is to the actual (true) value.

Let’s consider an example of temperature  sensor with an accuracy of ±2%.

When the temperature sensor is used to measure temperature in controlled temperature of 25°C.

Temperature sensor can show the values in the range of 24.5°C to 25.5°C.

Therefore accuracy of a product defines the deviation in measured value from actual value.

Precision

Precision defines the how close the measured values are to each other. Repeat-ability and reproducibility are two components of precision.

Let’s consider an example of measurement of block with micrometer. 

When a block of width 5 mm is measured 10 times and each time it is showing 5mm.  This means measurements are accurate and precise.

Whereas if micrometer is showing 4.5mm each time. This means measurement is not accurate but it is still precise.

Accuracy vs Precision

To understand the difference between accuracy and precision. Let’s consider an example of sportsperson hitting the bull’s eye with an arrow.

Accurate and Precise

Sportsperson is accurate and precise if all Arrows hit to center circle.

Accurate but Not Precise

If all arrow hits nearby center circle but are far away from one another. Sportsperson is accurate but not precise.

Precise but Not Accurate

If all arrow hits away from the center circle but are close to one another. Sportsperson is more precise but not accurate.

Neither Accurate nor Precise

Sportsperson is neither accurate nor precise. If all arrow hits away from the center and far from one another.

Conclusion

To sum up, Accuracy and precision plays a very important role in the measurement of outcome. They look very much similar. But it’s not correct. 

Got Questions?  We will be happy to help.

If you think we missed Something?  You can add to this article by sending message in the comment box. We will do our best to add it in this post.


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