Difference between Accuracy and Precision.

The words Accuracy and Precision are used in the context of measurement.

Precise means-to a fine degree of measurement. Accurate means the measurement is true.

Accuracy and Precision are two important points in measurements. In everyday language “accurate” and “precision” are roughly the same thing but not in Physics.

What is the importance?

Accuracy and Precision are very important for Instrumentation designers and maintenance personnel,  taken into consideration while selecting Instrumentation systems.

Precision is independent of accuracy.

Accuracy is independent of Precision.

Accuracy and precision are different points of view related to obtaining a correct measurement. It is possible to be accurate without being precise and be very precise but not very accurate. The below figure depicts the difference.

There is a number of ways to depict the difference between Accuracy and Precision.

The above figure explains what is precision and accuracy.

  • The dashed Redline is the actual temperature measurement with time.
  • Blueline is a measurement of the process variable that is accurate but not precise.
  • The magenta line is a measurement with precision but not accuracy.

What does Accuracy mean?

Accuracy is the degree to which there is no error in the sample. With words on the other hand, the less error there is in the sample, the more accurate the sample will be.  

Usually accuracy states how close the measured value is to the true value (True values) or the value that is considered correct (accepted value).

If there are no actual data or values ​​that are assumed to be correct then it is not possible to determine some of the accuracy of the measurement. Systematic error will have an impact on the accuracy of the measurement. If a systematic error occurs, the measurement accuracy cannot be increased by repeating the measurement.

Usually, the source of systematic error occurs because the measuring instrument is not calibrated or reading error (parallax error, for example).  

Accuracy is the degree of conformity of a measured quantity to its actual (true) value.

The accuracy of an experiment or object of value is a measure of how closely the experiment’s results agree with a true or accepted value.

Accuracy is defined as the degree to which the result of the measurement conforms to the correct value or a standard. After taking a lot of measurements you notice that they are very close to each other.

Accuracy refers to a particular value. Accuracy is defined as the extent to which a measured value agrees with a standard value. It tells that how close the measurements are to the true value.  

What does Precision mean?

Precision is measured by the standard deviation (Standard error).

Usually, precision states how close the result value is twice or more repeated measurements. The closer the value – the value of the repeated measurement results, the more precise the measurement is Random errors will have an impact on measurement precision.

Random errors present provide fluctuating measurement results, above and below the actual value or the value that is considered correct.

The measurement precision due to this random error can be improved by repeating the measurement. Usually, this error occurs due to problems in estimating measurement value when the needle is between two scale-lines or because the value indicated by the instrument fluctuates within a certain range.

Precision – is how successive measurements agree with each other.

Precision is the degree to which further measurements or calculations show the same or similar results. In other words, precision is a measure of the reliability of the experiment or how reproducible the experiment is.

Precision is the degree of exactness of different measurements that are repeatedly recorded.

Author: Neeraj