1. Statistical Methods in Water Resources

Second edition (2020) by Dennis R. Helsel, Robert M. Hirsch, Karen R. Ryberg, Stacey A. Archfield, and Edward J. Gilroy.
Now available for download as a free pdf textbook.

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Water resources data tend to have many variables with a lower bound of zero, tend to be more skewed than data from many other disciplines, commonly contain censored data (less than values), and assumptions that the data are normally distributed are not appropriate. Computer-intensive methods (bootstrapping and permutation tests) now improve upon and replace the dependence on t-intervals, t-tests, and analysis of variance. A new chapter on sampling design addresses questions such as “How many observations do I need?” The chapter also presents distribution-free methods to help plan sampling efforts. The trends chapter has been updated to include the WRTDS (Weighted Regressions on Time, Discharge, and Season) method for analysis of water-quality data. This new version contains updated graphics and updated guidance on the use of statistical techniques. The text utilizes R, a programming language and open-source software environment, for all exercises and most graphics, and the R code used to generate figures and examples is provided for download.
The second edition includes many of the methods used in our
Applied Environmental Statistics online course.


2. Statistics for Censored Environmental Data using Minitab and R

by Dennis R. Helsel
at market price from your favorite bookseller


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This second edition (2012) of the Nondetects And Data Analysis textbook (1st ed. 2004) introduces and explains methods for analyzing and interpreting censored ("nondetect") data in the environmental sciences. Adapting survival analysis techniques from other fields, the book translates well-established methods from other disciplines into new solutions for environmental studies. It applies methods of survival analysis, including methods for interval-censored data to the interpretation of low-level contaminants in environmental sciences and occupational health. New to the second edition is a chapter on multivariate methods for censored data, the use of interval-censored methods (especially for "remarked data" between the detection and quantitation limits), and expanded coverage of graphical methods for censored data. The basis for our Nondetects And Data Analysis online course and webinars.




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