Accuracy and precision with example & differences

We often hear the two words accuracy and precision during the measurement of a physical quantity in an experiment. Most of the students feel that these two terms have the same meaning. But these are much different from each other. In this article, we are going to discuss the concepts and differences between accuracy and precision with an example of experimental data. Errors are the causes of inaccuracy in measurement.

Contents in this article:

1. What is the accuracy of a measurement?
2. What is precision measurement?
3. Explanation of accuracy and precision with example of experimental data
4. Difference between accuracy and precision in a measurement

What is the accuracy of a measurement?

The accuracy in the measurement of a physical quantity indicates how close is the measured value of the physical quantity to its actual value or true value. To obtain greater accuracy, the average of the measured values should be very closer or nearly equal to the actual value of the physical quantity.

What is precision measurement?

Precision measurement of a physical quantity indicates how close are the measured values to each other. During the measurement of a physical quantity, we often measure more than once (usually we take three or five observations). If these data in all observations are very closer to each other then the measurement is a precision measurement. This is the basic concept and definition of precision in physics.

Explanation of accuracy and precision with an example of experimental data

Let, we want to measure the length of a rod whose actual length is 100.0 meters. Here, we are using a measuring scale that can measure up to one decimal. Three students individually measured the length of the rod with the same type of measuring scale. Measured data are shown in the table below –

No. of observation	Data of Student – 1	Data of student – 2	Data of student – 3
1	100.8	101.1	100.1
2	99.8	100.9	99.9
3	99.4	101.1	100.0
4	100.1	101.2	100.1
5	100.5	101.0	100.2

The average value of the data of student-1 is 100.1 meters which is very much closer to the actual value of 100.0 meters. So, the measurement of student-1 is accurate. But then if we look at the data carefully, we can see that the data are not closer to each other, they have wide differences by 1.4 meters, 1.1 meters, etc. So, the measured data of student-1 is not precise. Hence, the measurement of student-1 is accurate but not precise.

The average value of the data of student-2 is 101.1 meters which has a deviation of 1.1 meters from the actual value of 100.0 meters. So, the measurements of student-2 do not have good accuracy. But all measurements are very close to each other. The differences between the data are 0.1, 0.2, etc. So, the measurement of student-2 is a precision measurement.

Similarly, we can see that the measurement of student-3 has higher accuracy with good precision.

What is the difference between accuracy and precision?

The differences in accuracy and precision are as followings –

1. Any measurement closer to the actual value is an accurate measurement. If the measured values are closer to each other then the measurement is a precise measurement.
2. The accuracy of a measurement can be identified even after taking a single observation. But the precision of measurement can be identified only after taking two or more observations.
3. Systematic errors cause less accuracy. Random errors cause poor precision.

People also ask:

1. Difference between accuracy and precision in chemistry
2. The difference between accuracy and precision in physics
3. Difference of accuracy and precision
4. Accuracy and precision in measurement
5. Precision vs accuracy

This is all from this article on accuracy and precision of measurement and their differences. If you have any doubt on this topic you can ask me in the comment section.

Thank you!

Related posts:

1. Types of Errors in measurement
2. Rules to find number of significant figures