Define accuracy and precision
1) Accuracy: It is the closeness of an instrument reading with the true value of the quantity under measurement.
OR
It is defined as the ability of a instrument to respond to a true value of a measured variable under reference conditions.
2) Precision: It is measure of the reproducibility of the measurements; i. e. given a fixed value of a quantity, precision is a measure of the degree of agreement within a group of a measurement of the same quantity.