Jef L. Teugels

Maximum microbiological contaminant levels

Microbiological monitoring of drinking water for fecal contamination is a legal requirement in most countries. The objective is to protect the users from water borne disease. We expressed The United States Drinking Water Regulations (DWR) in statistical terms and examined their probabilistic characteristics both analytically and by simulations. The DWR set upper limits on the mean coliform count and on the individual counts of all samples examined per month. Our results show that only an upper limit on the mean coliform count is basically sufficient for DWR. Copyright

Trend Analysis of Extreme Values

In Dierckx and Teugels (Environmetrics 2:1–26) we concentrated on testing whether an instantaneous change occurs in the value of the extreme value index. This short article illustrates with an explicit example that in some cases the extreme value index seems to change gradually rather than instantaneously. To this end a moving Hill estimator is introduced. Further a change point analysis and a trend analysis are performed. With this last analysis it is investigated whether a linear trend appears in the extreme value index.