A modified statistical method for the detection of outlying values has been applied to five fortnightly sets of data from the National Quality Control Scheme. The overall outlier rate was 2·4 %, not varying greatly between analytes. Many of the outliers appear to be due to sample identification errors.
References
1.
BarnettV.LewisT. (1978). Outliers in statistical data, chapter 4. Wiley, Chichester.
2.
BurnettR. W. (1975). Accurate determinations of standard deviations for quantitative methods used in clinical chemistry. Clinical Chemistry, 21, 1935–1938.
3.
HealyM. J. R. (1978). A mean difference estimator of standard deviation in symmetrically censored Normal samples. Biometrika, 65, 643–646.
4.
HealyM. J. R. (1979). Outliers in clinical chemistry quality control schemes. Clinical Chemistry, 25, 675–677.
5.
WhiteheadT. P. (1977). Quality Control in Clinical Chemistry. New York, Wiley.
6.
WhiteheadT. P.BrowningD. M.GregoryA. (1975). A comparative survey of the results of analyses of blood serum in clinical chemistry laboratories in the United Kingdom. Journal of Clinical Pathology, 26, 435–445.
