# Compare between accuracy and precision

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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.

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