Measurement is an essential factor for us to understand the external world. Through millions of life years, we have developed a measurement sense. Measurements need tools, which provide a quantity for scientists. The problem that occurs here is, the result of every measurement by any measuring instrument contains a sort of uncertainty, where this uncertainty is called an Error.
Accuracy and precision are more essential factors to consider while taking any measurements. These terms explain how close a measurement is to either a known or accepted value. Let us look at precision, accuracy, and their differences in detail.
Accuracy
Accuracy can be explained as the ability of an instrument to measure the accurate value. In other terms, the closeness of the measured value to a true or standard value. Accuracy is obtained by taking small readings, and these small readings reduce the calculation error. The accuracy of the system has been classified into three types as given below.
Point Accuracy
The accuracy of an instrument only at a particular point on its scale is called point accuracy. It is quite important to make a note; this accuracy does not give any info on the general accuracy of the instrument.
Accuracy as the Percentage of Scale Range
The uniform scale range defines the accuracy of a measurement. We can understand this better with the help of the below example:
Let us consider a clinical thermometer having a scale range of up to 5000 C. The thermometer has an accuracy of ±0.5; it means ±0.5 percent of increase or decrease in the instrument value, which is negligible. But if the same reading is more or less than 0.50 C, it is considered as a high-value error.
Accuracy as the Percentage of True Value
This type of accuracy of the instrument is defined by identifying the measured value with regards to their true value. The instruments’ accuracy can be neglected up to ±0.5 percent from the true value.
Precision
The closeness of either two or more measurements to each other is called the precision of a substance. If a given substance is weighed five times and gets 3.2 kg every time, the measurement is very precise but not necessarily accurate. Precision is always independent of accuracy. The example discussed below will explain to you how you can be precise but not accurate and vice versa. Precision can sometimes be separated as follows.
Repeatability
This is the variation, arising when the conditions are kept identical, and repeated measurements are taken in a short period of time.
ReproducibilityIt is the variation, arisen when using the same measurement process among different operators and instruments and over longer time periods.
Example of Accuracy and Precision
There are many real-time examples that can be discussed in the concept of Accuracy and Precision. Let us discuss one among them.
Let us go through a good analogy to understand the difference between precision and accuracy with an example. Imagine if a football player is shooting at the goal. If the player shoots the ball into the goal, he is said to be accurate. Also, a football player who keeps striking the same goalpost is precise but not accurate.
Thus, a football player can be accurate without being precise if he hits the ball all over the place but still, he scores. Also, a precise player will hit the ball to the same spot repeatedly, irrespective of whether or not he scores. A football player, who is accurate and precise, will not only aim at a single spot but also score a goal.
Considering the image, the image on the top left shows the target hit at a high precision point and accuracy. The image on the top right shows the target hit with high accuracy but low precision. The image listed on the bottom left shows the target hit at a high precision but with low accuracy. Finally, the image placed on the bottom right shows the target hit at low accuracy and at low precision.
List Out the Difference Between Accuracy and Precision in Tabular Form
The difference between accuracy and precision is tabulated below:
|
Accuracy |
Precision |
|
Accuracy is the level of agreement between the absolute measurement and the actual measurement. |
Precision implies the variation level that lies in the values of several measurements of a similar factor. |
|
It represents how the results agree with the standard value closely. |
It represents how the results closely agree with one another. |
|
Accuracy is a single-factor or measurement. |
Here, multiple measurements or factors are needed. |
|
Possibly, a measurement can be accurate on occasion as a fluke. But, for a measurement to be accurate consistently, it should also be precise. |
The results can be precise without being accurate. And, alternatively, the results can be accurate and precise. |
|
Accuracy is not dependent on precision. |
Precision is not dependent on accuracy. |
Accuracy and precision are tools used in measurement, this topic is briefly discussed in chapter 2 called units and measurement of the class 11 NCERT book. This chapter is prescribed by the Central Board of Secondary Education and it forms the basis of chemistry. Students preparing for NEET should get a clear foundation of the basic concepts that are taught in classes 11 and 12 as some extremely important questions can be asked in the NEET exam.
Measurement of physical quantities needs a comparison with a certain arbitrarily chosen, basic, internationally accepted method or reference standard called unit. Measurement is considered the basic foundation of all experimental science and technology. There is some form of uncertainty in the result of every measurement taken by any measuring instrument. This uncertainty can be termed as an error. Even calculated quantities which are based on measured values have some form of error. This is where the difference between accuracy and precision comes into existence.
Accuracy can be defined as the measure of how close the measured value is to the true value of the quantity. On the other hand, precision can be defined as the quality of being exact. It refers to how close two or more measurements are to each other, regardless of their accuracy, in some cases it is possible for precise measurements to not have accuracy.
The study notes provided by on The difference between accuracy and precision are extremely important in the study of measurement, measurement forms the basis of chemistry and without it, experiments can’t be performed. Therefore, students who aspire to study further in this field should have their basics cleared. The difference between accuracy and precision is briefly discussed in the class 11th chapter, however, has created separate study notes that are related only to the study of the topic being discussed. The topi
cs are taken separately and explained because it helps to get a better understanding of the concept and also it covers all the minute details that may be missed by students otherwise.
Both accuracy and precision help to determine how close measurement is to an actual value, however, both these concepts are not the same. Accuracy represents how close a measurement is to the actual value, on the other hand, precision represents if the measurements are reproducible or not even if they are far from the actual value. Both precise and accurate measurements are close to the true values and are also repeatable.
Accuracy and precision are terms in chemistry that have a critical meaning in science and they are constantly used incorrectly. Therefore it is extremely important to know their workings.
Important Concepts that Help to Understand the Difference between Accuracy and Precision
2.2 The international system of units
2.3 Measurement of length
2.4 Measurement of mass
2.5 Measurement of time
2.6 Accuracy, the precision of instruments and errors in measurement
2.7 Significant figures
2.8 Dimensions of physical quantities
2.9 Dimensional formulae and dimensional equations
2.10 Dimensional analysis and its applications