Content Curator
The difference between Accuracy and Precision is that Accuracy is the degree of closeness to true value whereas precision determines the degree to which an instrument or process would repeat the same value.
- Accuracy and precision are considered the two forms of measurement that define how close you are to achieving a goal.
- Simply, high accuracy can be achieved when you directly land on your target value.
- However, low accuracy is when you are not close to hitting the target aimed for.
- Precision, on the other hand, is how close your results are to each other.
- While accuracy is expressed by means of absolute error and relative error, precision uses absolute deviation and relative deviation.
Measurements need tools which offer scientists with quantity. However, the result of each measurement by means of a measuring instrument comprises some uncertainty. This uncertainty is termed an error.
| Table of Content |
Key Terms: Accuracy, Precision, Relative Deviation, Absolute Deviation, Relative Error, Absolute Error, Percentage, Variation
What is Accuracy?
[Click Here for Previous Year Questions]
Accuracy refers to measuring how close a value from a measurement is to the true value or the standard. In terms of instruments, accuracy dictates the ability of any instrument to measure close to the standard value. Generally, experts obtain small readings from an instrument. They are then combined to lessen errors in the calculation. Accuracy can simply be defined as:
| “The closeness of the measured value to a true or standard value. Accuracy can be obtained by taking small readings” |
In the case of Accuracy, the small readings help reduce the error of calculation. The accuracy of a given system can be classified into three types:
- Point Accuracy
- Percentage Accuracy
- Accuracy as a Percentage of True Value
Significant Figures Video Lecture
Types of Accuracy
[Click Here for Sample Questions]
Accuracy when calculated is of three types. They are as follows.
Point Accuracy
Point accuracy refers to the accuracy of an instrument at one particular point on the scale. This accuracy is not the same as general accuracy.
Percentage Accuracy
Accuracy as a percentage of scale range or percentage accuracy is obtained by multiplying the accuracy percentage by the pressure reading. Lower the pressure measurement figure, and the accuracy would be much better.
Accuracy as a Percentage of True Value
This type of accuracy is derived by calculating the true value with its true value. Generally, errors of 0.5 plus or minus, are ignored when calculating the accuracy of an instrument.
What is Precision?
[Click Here for Sample Questions]
Precision is a measure of exactness. It refers to how close two or more measurements are to each other. These measurements might not be accurate as accuracy is independent of precision.
Accuracy and Precision
For example, If you weigh an object five times and acquire 3.2 kg each time after weighing, then the measurement taken is precise but not necessarily accurate. Precision is typically independent of accuracy.
Precision can be further divided into two parts:
- Repeatability
- Reproducibility
Solved ExamplesQues. 20.5 mL is the volume of a given liquid. Which among the listed sets of measurements represents the value with good accuracy? Ques. If a man shoots a ball into the goal within just one shot, then is his action accurate or precise? Ans. The man here is said to be accurate. |
Types of Precision
[Click Here for Previous Year Questions]
Precision can be of two types. They have been described below:
Repeatability
Repeatability is a precision measurement variation that is done when the conditions are kept identical. In the case of Repeatability, it should fulfill the following conditions:
- Same place
- By the same person
- With the same method
- On the same equipment
- Over a short time period
Repeatability can be defined as the variation in readings when the same individual measures the same portion multiple times using the same equipment and method under the same conditions.
Example of Repeatability
Assume that an individual keeps measuring repeated readings of a substance by micrometre as 15.01 mm, 15.02 mm, and 15.01 mm. This means the person can potentially repeat their readings, with the competence level being high.
Reproducibility
The opposite of repeatability is reproducibility. Under this condition, variations arise when the same measurement process is used over different instruments and also operators. This process is done over a long period of time as compared to repeatability which takes place over a short period of time.
- Different place
- By different person
- With different method
- On different equipment
- Different time
Example of Reproducibility
If three different people calculate and measure the reading of the same object by micrometre giving 15.54 mm,15.64 mm, 15.49 mm, then the reproducibility of this measurement is considered to be 0.15 mm.
Read More: Significant Figures
Difference between Accuracy and Precision
[Click Here for Previous Year Questions]
The differences between Accuracy and Precision are tabulated below:
| Type of Difference | Accuracy | Precision |
|---|---|---|
| Meaning | Accuracy is how close a derived measurement is to the standard or true value of the instrument. | Precision is the variation between the measurements of the same factor relation. |
| Relation between Measurement | Accuracy is how close the measurement is to the true value. | Precision is how two calculated measurements are to each other |
| Measurements | Measurements in accuracy can be accurate but not precise. | Measurement can be precise in precision but not accurate. |
| Number of Measurements | Accuracy is fixed through a single measurement. | Precision is calculated through multiple measurements. |
| Errors | Accuracy is affected due to systemic errors. | Precision is affected by random errors. |
| Correctness | Most accuracy measurements are precise. | Most precision measurements may not be precise. |
Examples of Accuracy and Precision
[Click Here for Sample Questions]
Precision can be defined as how reliable a particular measurement of an experiment is. On the other hand, accuracy checks how close the experiment’s measurement is to the standard or the accepted value. The differences between both terms can be illustrated through the example below.
- Imagine hitting a dartboard with the target in the middle of the board.
- Accuracy would be when all the darts are hit near the centre of the target.
- The hits could be on different sides and in and around the centre of the target.
- Thereafter, the precision would be if all the dart hits are closely done.
- This cluster of dart hits can also be away from the centre of the dart board.
Previous Year Questions
- A screw gauge has least count of 0.01 mm and there are… [NEET 2020]
- The dimensions of impulse are equal to that of… [NEET 1996]
- Lumen is the unit of…. [UPSEE 2019]
- A plate has a length 5… [KEAM 2003]
- A body weighs 22.42 g and … [WBJEE 2010]
- Which of the following dimensions will be the same … [NEET 1996]
- A certain body weighs 22.42g and has a measured volume of… [NEET 1991]
- Planck’s constant (h), speed of light in vacuum (c) and Newton’s gravitational constant (G) are… [NEET 2016]
- A physical quantity of the dimensions of length that can be formed out of… [NEET 2017]
- The dimensional formula of angular momentum is… [NEET 1988]
Things to Remember
- Accuracy determines how closely the measured value of a quantity corresponds to its “actual” value.
- Precision indicates a degree of reproducibility or agreement between repeated measurements.
- More measurements lead to better precision, and eventually, a smaller error will occur.
- Precision can be divided into two categories, namely Repeatability and Reproducibility.
- Accuracy can be classified into three categories, namely Point Accuracy, Percentage Accuracy and Accuracy as a Percentage of True Value.
Also Read:
| Chapter Related Concepts | ||
|---|---|---|
| Precision | Sampling Error | Cisplatin |
| Uses of Vernier Calipers | Absolute and Relative Error | Dimensional Analysis |
Sample Questions
Ques. What are Accuracy and Precision? (1 Mark)
Ans. Accuracy measures how close the instrument measurement is to the set standard value. Precision is, on the other hand, how close or related two measurements are to each other.
Ques. A liquid’s volume is 26 mL. A student then measures the volume, thus determining it to be 26.2 mL, 26.1 mL, 25.9 mL, and 26.3 mL in the first, second, third, and fourth trials, respectively. Thus determine which among the following statements is true for his measurements.
a. They have poor precision.
b. They have poor accuracy.
c. They have good precision.
d. They are neither precise nor accurate. (1 Mark)
Ans: They have good precision.
Ques. What is error? (1 Mark)
Ans. Error is the difference between the true and calculated values from the experiment.
Ques. What are some examples of Accuracy and Precision? (1 Mark)
Ans. A good example of both Accuracy and Precision can be done through a football player. If the said football player can successfully hit the ball into the goal, that is accuracy. On the other hand, if the player is hitting the goalpost repeatedly, that is precision.
Ques. How is Precision determined? (3 Marks)
Ans. Precision calculation is easier than accuracy. The steps to do so are as below.
- Take the data for which the calculation is to be done.
- Sort it and take the maximum and minimum values.
- Take the difference between both to arrive at the final value.
Ques. How is Accuracy calculated? (3 Marks)
Ans. Accuracy can be calculated through the following steps.
- Gather the calculated value or measurement from the experiment.
- Take the standard or the accepted value.
- Calculate the difference between both figures.
- Calculate the results with the true or standard value to arrive at the final answer.
Ques. What are the major differences between Accuracy and Precision? (3 Marks)
Ans. The differences between accuracy and precision are as follows.
- Accuracy is the difference between the true value and the calculated value. Precision is a measure of how close two calculated values are.
- Accuracy is a single measurement but precision measurement is done several times.
- Systematic errors affect accuracy and random errors affect precision.
Ques. How to calculate error? (4 Marks)
Ans. The process to calculate errors is as follows:
- Take the standard value and the experimental value.
- Calculate the difference between both values.
- Divide the result by the standard value and multiply it by 100.
- The result is an error percentage.
Ques. What are the types of Accuracy and Precision? (5 Marks)
Ans. Accuracy and precision are the two forms of measurement which exhibit how close you are to achieving a goal. Accuracy is referred to the measurement of how close a value from a measurement is to the true value or the standard. Accuracy has been classified into three categories:
- Point Accuracy
- Percentage Accuracy
- Accuracy as a percentage of true value
Precision can be expressed as how reliable a specific measurement of an experiment is.
Precision is of two types. They are listed below.
- Repeatability
- Reproducibility
Also Read:
Comments