Accuracy, Precision of Instruments, and Errors

Measurement is crucial in order to understand the world. For years, we have developed different methods to measure things with accuracy & precision. Measurement requires tools that can provide scientists with results that have precision and accuracy. The problem arises when the result of measuring tools has some uncertainty. This uncertainty issue is called an error. Therefore, precision and accuracy are crucial yardsticks of measurements. These terms have their importance in the measurement concept to know how close the experimental value (value one gets in an experiment) is  to the accepted or true value.  

Accuracy is called the ability to measure the accurate value of a measuring instrument. In other words, it is the accepted value of the measured value to an actual or standard value. Accuracy is measured by taking small readings that can reduce the error in calculation.

The accuracy of the system is divided into three types, as follows:

1.     Point Accuracy:

The accuracy at a particular point with a measuring instrument on its scale is called point accuracy. It is crucial to understand that this accuracy does not give information about general accuracy about the measuring tools.

2.     Accuracy of scale range as a percentage:

The accuracy of measurement can be better understood with the help of accuracy and precision examples:

Consider a thermometer having a scale range of 500ºC and the thermometer having an accuracy of ±0.5, i.e., an increase in ±0.5 percent or decrease in the ±0.5 percent of the value is considered negligible. But if the reading value is more or less than 0.5ºC, it is a high-value error.

3. Accuracy of True Value as Percentage:

The accuracy of measuring value is identified with the help of a measuring instrument. The accuracy of the measuring instrument is negligible, up to ±0.5 percent from the actual value. 

Precision:

Precision is a measure of the closeness of the measured value from the true value. It is measured in terms of accuracy and it measures the closeness or closeness of the measured value to the accepted or true value. The solution for measuring an instrument gives us a result that has a small estimation error and gives us the best possible accuracy, which is called precision.

To understand precision, it is important to understand its meanings with different categories:

1. Precision:

The point precision indicates how closely a single reading can be calculated compared with another reading at a particular point. Point precision relates to one-point accuracy.

2.     Scale Range Precision:

Scale range precision is a concept that involves the consideration of accuracy and precision of reading and measuring instruments. Scale range precision shows how close the values are compared with the accepted value.

3.     True Value Precision:

The true value precision indicates the magnitude of difference between two values at the same time. It gives information about errors in between two readings that are calculated about a measuring instrument or system. Precision is very significant for every experiment, because it involves accuracy and also helps to calculate uncertainty, which is based on systematic errors only (error propagated from source to source).

 The closeness of the two or more measurements is known as the precision of an object. If you measure an object five times and get 2 kg every time, the measuring value has precision, but accuracy is not necessarily present or can be vice versa.  There are two components of Precision measurement. They are:

1. Repeatability:

This refers to the measurement of the same object again, and the value of the object is measured to be the same for all the five readings. Repeatability is a measurement of how closely an object is measured in the same way for a single measurement. The variation arises when the conditions are the same, but repeated measurements are considered short.

2. Reproducibility:

Reproducibility measures the closeness of the different measurements that are repeated with an object, or if someone else measures it, they get similar readings. The difference occurs when different operators and instruments use the same measurement process over a more extended period.

3. Uncertainty:

Uncertainty is not only associated with all basic units to estimate the error but it is also very important to understand that a more diverse and wider unit has larger uncertainty than a smaller unit. If we suppose that we are measuring something with a mass scale, then the uncertainty will be greater than a length measurement.

Difference Between Precision and Accuracy:

In the previous section, we understood the basics of Accuracy, Precision of Instruments, and Errors. Let us take a look at the difference in precision and accuracy.

Accuracy and Precision Examples:

An example for understanding precision and accuracy is taking thermometer readings. When a weather thermometer reads 68 degrees Fahrenheit outside and it is really 68 degrees Fahrenheit, the thermometer is said to be accurate. If the thermometer registers the same temperature repeatedly for the next few days, the thermometer can also be called precise.

More Accuracy and Precision Examples:

If you measure the body’s mass of 20kg and get 17.4, the measuring tool is precise but inaccurate. But if it gives 20.5, it is more accurate and less precise.

False Precision:

When exact numbers are used to express abstract ideas, it is known as “false precision”.  In daily life, the “false precision” can be understood through the statement given below. 

1. i) “90 percent of the hard work will start from the next season”. 
2. ii) “Our product is twice as healthy as any other competitors.”

One can say that false precision can be used to make false claims in marketing. 

It has been found that in most scientific experiments, unintended false precision can creep in if both the high-precision and low-precision data are combined because there can be inequality in the conversion from one system of unit to another. 

 Conclusion:

Accuracy and precision are two terms that are often confused by people. In this article, we have learned the difference between accuracy and precision as well as a few examples that can help a person to understand these concepts better. Accuracy has to do with a comparison of the results of the instrument’s readings with one another. Precision has to do with the difference in the values of an instrument’s readings for repeating a set of measurements. Precision and accuracy examples have given a clearer picture about this crucial concept. The topic Accuracy and Precision Examples is important from the exam’s point of view.