title: Detection of drift effects before calculating the standard deviation as a measure of analytical imprecision.
abstract: The sample standard deviation is commonly used as a measure of analytical imprecision, calculated from a series of n data obtained from one sample split for n assays. Drift effects cause an overestimation and consequently a misinterpretation of the standard deviation in clinical chemistry. The r-ratio test is recommended as a simple procedure for detecting drift effects. It has been found necessary to eliminate outliers before drift effects can be recognized.
mesh_terms: D000704:Analysis of Variance; D002624:Chemistry, Clinical / Q000592:standards*; D006801:Humans; D013223:Statistics as Topic