Units and Measurement

Precision Definition and Examples

Definition of Precision

Precision is the amount of information whose conveyance takes place by a number in terms of its digits. Precision shows the closeness of two or more measurements that they have to each other. It is certainly different from accuracy.

Accuracy refers to the closeness of the measurements related to a specific value. Furthermore, accuracy is the description of the systematic error. Moreover, accuracy gives us the measure of the statistical bias.

Examples of Precision

Example 1 – 

When you are measuring the value of resistance using a digital multimeter. The value of resistance is actually 35 Ohms, but multimeter is showing 33 Ohms consistently 10 times. So, Multimeter is Precise but not Accurate.

Example 2 – 

Let’s say the temperature of an object is 60-degree celsius. And thermometer is showing 60 degrees for all readings. That means thermometer is Accurate and precise.


Difference between Accuracy and Precision

We have often statements like a spot on and bullseye. These statements usually come when one guesses the right answer to a question. Similar to this quiz, the accuracy of data shows how close a measurement is to the ‘true’ value.

Let’s consider the bullseye for example. If one hits the target that one was throwing darts at, and the very center of the target is hit, one would be considered very accurate because that is the ‘true’ value.

However, in case one hits outside the center of the target each time, one would be considered inaccurate because it is not near the ‘true’ value. So, the farther one is from the center, the lesser will be the accuracy.

Accuracy is very important when it comes to data collection. For example, one may wish to measure a certain chemical’s volume in the experiment.

If the actual volume was 60 ml but the measurement was 75 ml, it would not be a very accurate value due to the fact that it is not close to the ‘true’ value of 60 ml. However, if the measurement is of 59 ml, one may consider this as an accurate value because of its immense closeness to the ‘true’ volume.

Now let us go back to the target. This time, when throwing off the darts takes place, the hit is nowhere near the centre. However, one hits the same spot every time.

In this case, the person was not accurate but rather precise. This is because precision refers to the agreement of repeated measures.

Hence, while accuracy shows how close one was to the true value, precision shows how often one would get the same measurement under the same conditions. Experts often call precision as the reproducibility or repeatability.

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Importance of Precision and Accuracy

Both accuracy and precision happen to be equally important for the purpose of attaining the highest quality measurement possible. In order to ensure that a set of measurements be precise, there is no requirement that it be accurate at all. This happens because a series of measurements will be precise as long as they are grouped together in value.

However, there is no requirement that the value they are grouped around must be close to the item’s true value being measured. Due to this, sometimes the valuation of accuracy takes place over precision. This is because it can be more useful in the determination of needed value.

However, when it comes to the maintenance of a measurement system, checking of the system must take place regularly for both accuracy and precision. This is because they both happen to be equally important for measurement success.

Solved Question for You

Question 1: Briefly differentiate between accuracy and precision?

Answer: Precision refers to the amount of information whose conveyance takes place by a number in terms of its digits. It reflects the closeness between two or more measurements. In contrast, Accuracy refers to the closeness of the measurements that are related to a specific value and it is the description of the systematic error.

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