Trend Analysis for Data w/ NDs
Never substitute fractions of the detection limit
A free-to-stream video that is a taste of our course Nondetects And Data Analysis.
Concentrations of trace contaminants often have a significant percentage of nondetects, data below the detection or quantitation limits of the laboratory used. Are those concentrations at a site changing over time? This video will demonstrate the equivalents of the Mann-Kendall test, Seasonal Kendall test, and regression methods for data with nondetects. Methods for data with multiple detection limits are included.
Dennis Helsel (Ph.D. Environmental Science and Engineering):
"I'm a translator of statistical methods for scientists. My firm's name, Practical Stats, says it all. I've written/co-authored two textbooks. Statistics for Censored Environmental Data using Minitab and R (2012) pioneered statistical methods for data below detection limits. Statistical Methods in Water Resources (2020) has been cited by scientists throughout the world. I've taught webinars for the National Water Quality Monitoring Council and others; workshops for the American Statistical Association and others; courses such as AES and NADA for scientists in North America, Europe and Singapore since 1990. I worked for 30 years at the US Geological Survey before starting Practical Stats.
In 2003 I received the Distinguished Achievement Award from the American Statistical Association’s Section on Statistics and the Environment for my training courses in applied statistics.
In 2018 I received the Lifetime Achievement Award from the California Groundwater Resources Association for my communication of statistical methods to scientists. My courses provide up-to-date procedures communicated in clear language using video examples of data analysis of 'real data'."