The AHS is currently offering the following workshop for the 2011 Symposium

Measurements of trace chemicals in environmental media (water, air, soils, biota) frequently result in values reported only as less than the laboratory reporting limit (“less-thans”, “nondetects”, and “qualified values”). The most commonly used method for incorporating nondetects is to substitute one-half the reporting limit and continue as usual. Unfortunately, this approach may obscure patterns and trends that are present or create patterns and trends that are not actually present in the original data. This approach is fraught with error. Two easily implemented methods that avoid the problems with substitution produce summary statistics (mean, median), perform hypothesis tests, and compute regression models for data with nondetects. These will be discussed in detail. More complex procedures from the field of survival analysis will also be introduced. These procedures explicitly handle data with multiple detection limits. This workshop is based on Dr. Helsel’s new textbook Statistics for Censored Environmental Data (first edition was titled Nondetects And Data Analysis), published by Wiley. A CD including a presentation file and other relevant materials will be provided at the workshop.

To register for this workshop visit the registration page at Event Interface: http://www.eventinterface.com/2011AHS_Symposium

Dr. Helsel will also be teaching a 2 day class at the USGS Flagstaff Science Center September 21-22, 2011 "Untangling Multivariate Relationships (UMR)". Information about the class can be viewed at this web site: http://www.practicalstats.com/new_classes/classes.html

**Save $145 on the two day class for anyone also attending the AHS Symposium!

For additional information or questions, please visit the Practical Stats website http://www.practicalstats.com or contact Mike Tomlinson at tomlinson86@q.com.