A quality control method for routine analytical laboratories is presented, that consists of testing the results of a control sample according to their probability of occurrence and on being approximations of the results previously obtained for the sample. The method is unbiased, easily automated, and can be applied to all analyses performed on the same control sample, even for those in which the mean and standard deviation are erroneously estimated due to the use of insufficient significant figures for expressing the results.
quality control; routine analytical laboratories; non-parametric method