Matched Pair Tests

for Data With Nondetects

Paired differences such as concentrations Before/After a treatment at a series of sites or Upstream/Downstream of an outfall at several points in time are usually analyzed for change with a paired t-test (parametric) or signed-rank test (nonparametric). But what methods can be used when data include values below detection or quantitation limits without substitution of numbers for nondetects? This video will present what methods are available and demonstrate their use with R software.

This is a taste of the course material found in greater detail in our Nondetects And Data Analysis course.


Your Instructor


Dennis Helsel
Dennis Helsel

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'."


Course Curriculum


  Matched Pair Tests for Data With Nondetects
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