Statistics Meeting Book (May 15, 2019)

4. PRECISION 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. 4 4.1. Repeatability Repeatability expresses the precision under the same operating conditions over a short interval of time. Repeatability is also termed intra-assay precision . 4.2. Intermediate precision Intermediate precision expresses within-laboratories variations: different days, different analysts, different equipment, etc. 4.3. Reproducibility Reproducibility expresses the precision between laboratories (collaborative studies, usually applied to standardization of methodology).

AMC Technical Brief http://www.rsc.org/images/terminology-part-1-technical-brief-13_tcm18-214863.pdf I recommend you download the document for the full discussion.

Precision Precision The closeness of agreement between independent test results obtained under stipulated conditions. Notes – 1. Precision depends only on the distribution of random errors and does not relate to the true value or the specified value. 2. The measure of precision usually is expressed in terms of imprecision and computed as a standard deviation of the test results. Less precision is reflected by a larger standard deviation. 3. Independent test results means results obtained in a manner not influenced by any previous results on the same or similar test object. Quantitative measures of precision depend critically on the stipulated conditions. Repeatability and reproducibility conditions are particular sets of extreme stipulated conditions. [ISO 3534: 3.14]