Explain the consept of accuracy and precision
Answers
Explanation:
Accuracy
The ability of the instrument to measure the accurate value is known as accuracy. In other words, the closeness of the measured value to a standard or true value. Accuracy is obtained by taking small readings. The small reading reduces the error of the calculation. The accuracy of the system is classified into three types as follows:
Point Accuracy
The accuracy of the instrument only at a particular point on its scale is known as point accuracy. It is important to note that this accuracy does not give any information about the general accuracy of the instrument.
Accuracy as Percentage of Scale Range
The uniform scale range determines the accuracy of a measurement. This can be better understood with the help of the following example:
Consider a thermometer having the scale range up to 500ºC. The thermometer has an accuracy of ±0.5, i.e. ±0.5 percent of increase or decrease in the value of the instrument is negligible. But if the reading is more or less than 0.5ºC, it is considered a high-value error.
Accuracy as Percentage of True Value
Such type of accuracy of the instruments is determined by identifying the measured value regarding their true value. The accuracy of the instruments is neglected up to ±0.5 percent from the true value.
Precision
The closeness of two or more measurements to each other is known as the precision of a substance. If you weigh a given substance five times and get 3.2 kg each time, then your measurement is very precise but not necessarily accurate. Precision is independent of accuracy. The below example will tell you about how you can be precise but not accurate and vice versa. Precision is sometimes separated into:
Repeatability
The variation arising when the conditions are kept identical and repeated measurements are taken during a short time period.
Reproducibility
The variation arises using the same measurement process among different instruments and operators, and over longer time periods.