Compare between accuracy and precision
Accuracy
|
Precision
|
It is the closeness which an instrument reading approaches the true value of the quantity being measured. OR The degree of exactness of a measurement compared to the expected value.
|
It is the ability of the instrument to reproduce a certain set of readings with a given accuracy. OR A measure of the consistency of measurements, i.e successive readings do not defer.
|
It represents the nearness of the measurement with actual value.
|
Precision represents the nearness of an individual measurement with those of others
|
It is a measure of statistical bias
|
It is a measure of statistical variability.
|
It is based on single factor
|
based on multiple factors
|
It is concerned with systematic error that is error due to problems in instrument.
|
It is concerned with random error which occurs periodically with no recognizable pattern.
|
Example : The accuracy of a thermometer having a range of 5000C may be expressed as ±0.5% of scale range. This means that the accuracy of the thermometer when the reading is 5000C is ± 0.5%.
|
Example: Consider the measurement of a known voltage of 100V with a voltmeter. Five readings are taken, and the indicated values are 104,103,105,103 and 105V. From these values, it is seen that the instrument has a precision of ±1% since the maximum deviation from the mean reading of 104V is only 1.0V.
|
Parameter
|
Accuracy
|
Precision
|
Definition
|
The degree of conformity and correctness of something when compared to a true or absolute value.
|
A state of strict exactness — how often something is strictly exact.
|
Measurements
|
Single factor or measurement
|
Multiple measurements or factors are needed
|
Relationship
|
Something can be accurate on occasion as a fluke. For something to be consistently and reliably accurate, it must also be precise.
|
Results can be precise without being accurate. Alternatively, results can be precise AND accurate.
|
Uses
|
Physics, chemistry, engineering, statistics, and so on.
|
Physics, chemistry, engineering, statistics, and so on.
|