# Accuracy and Precision

In this article, we will see the difference between accuracy and precision terms. They are also most confusing terms in measurements regarding instruments.

Contents

## What is Accuracy?

Accuracy is the closeness with which the instrument reading reaches the true value of the quantity being measured.

1. The accuracy of measurement means conformity to truth.
2. The accuracy can be improved.
3. Accuracy simply depends upon the techniques of analysis.
4. Accuracy is necessary but not sufficient condition for precision.

## What is Precision?

Precision is a measure of reproducibility of the measurement, i.e. given a fixed value of a quantity or the degree of exactness for which instrument is designed or intended to perform.

1. Precise means clearly or sharply defined.
2. Precision cannot be improved.
3. Precision requires many sophisticated techniques of analysis.
4. Precision is necessary but not sufficient condition for Accuracy.

## Difference between Accuracy and Precision

The difference between Accuracy and Precision can be better understood from below common example of target shooting experiment. The intended goal is to target dart-board center.

Case-1: You send four darts flying toward the board and they all hit away from the center. But all darts are close to each other as shown in Fig 1(a).

The throw (in total) you made is neither precise nor accurate (low precision and not accurate).

So, let’s try again.

Case-2: You send four new darts flying toward the board and they all hit near to the center. But all darts are close to each other as shown in Fig 1(b).

The throw (in total) you made is less accurate with low precision.

So, let’s try again.

Case-3: You send four new darts flying toward the board and they all hit away from the center. But all darts hit almost at the same position as shown in Fig 1(c).

The throw (in total) you made is not accurate but has high precision.

So, let’s try again.

Case-4: You send four new darts flying toward the board and they all hit near the center. But all darts hit almost at the same position as shown in Fig 1(d).

The throw (in total) you made is accurate with high precision.

 S.No. Accuracy Precision 1. It is the closeness with the true value of the quantity being measured. It is a measure of reproducibility of the measurements. 2. The accuracy of measurement means conformity to truth. The term precise means clearly or sharply defined. 3. Accuracy can be improved. Precision can not be improved. 4. It depends upon simple techniques of analysis. It depends upon many factors and requires many sophisticated techniques of analysis. 5. Accuracy is necessary but not sufficient condition for precision. Precision is necessary but not a sufficient condition for accuracy. 6. Accuracy means setting a result that is close to the real answer. Precision means getting a similar result every time you perform measurement.

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