Accuracy Vs Precision
in Analytical Method Validation
Sunday, 31 January 2016
Accuracy Vs Precision in Analytical Method Validation
People are always a little confused about analytical validation characteristics like accuracy, precision, intermediate precision, repeatability and reproducibility. Can some differentiate these to terms?
Accuracy is defined as the degree of exactness, and precision means the degree of reproducibility.
The accuracy of an analytical procedure expresses the closeness of agreement between the value which is accepted either as a conventional true value or an accepted reference value and the value found. This is sometimes termed trueness.
The precision of an analytical procedure expresses the closeness of agreement (degree of scatter) between a series of measurements obtained from multiple sampling of the same homogeneous sample under the prescribed conditions. Precision may be considered at three levels: repeatability, intermediate precision and reproducibility. Precision should be investigated using homogeneous, authentic samples. However, if it is not possible to obtain a homogeneous sample it may be investigated using artificially prepared samples or a sample solution. The precision of an analytical procedure is usually expressed as the variance, standard deviation or coefficient of variation of a series of measurements.
Repeatability expresses the precision under the same operating conditions over a short interval of time. Repeatability is also termed intra-assay precision.
Intermediate precision expresses within-laboratories variations: different days, different analysts, different equipment, etc.
Reproducibility expresses the precision between laboratories (collaborative studies, usually applied to standardization of methodology).