Precision: Precision is the measure of the degree of repeatability of an analytical method under normal operation and is normally expressed as the percent relative standard deviation for a statistically significant number of samples.

The two most common precision measures are 'repeatability' and 'reproducibility'. These are expression of two extreme measure of precision which can be obtained. Repeatability (the smallest expected precision) will give an idea of the sort of variability to be expected when a method is performed by a single analyst on one piece of equipment over a short time scale. If a sample is analyzed by a number of laboratories for comparative purposes then a more meaningful precision measure to use is reproducibility ( this is the largest measure of precision).

In practice the laboratory is usually interested in the extent of variability which occurs over time when it operates the method. This is called 'intermediate precision' and describes the variability when the method is deployed in the same laboratory, perhaps on different pieces of equipment, and using different analysts on the staff. It is expected that this will give a value between repeatability and reproducibility.

Source : labnetwork.org

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