The measurement of trace chemicals in water, air, soil, and biota frequently results in values reported only as less than the detection limit.

The standard practice in environmental science for interpreting these data is woefully inadequate, usually consisting of substituting one-half the detection limit and performing traditional statistics tests.

Offering a unique approach, Nondetects and Data Analysis presents methods that are widely used in medical and industrial settings but have been rarely or never applied to issues of environmental health.

The steps necessary to take these existing procedures and apply them to left-censored environmental data are fully illustrated.

Contents:

1. In focus
2. The three approaches
3. Reporting limits
4. Storing data in databases
5. Plotting data with nondetects
6. Computing summary statistics
7. Computing interval estimates
8. What can be done when all data are below the reporting limit?
9. Comparing two groups
10. Comparing three or more groups
11. Correlation
12. Regression and trends

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ORDER NOW Nondetects and Data Analysis Statistics for Censored Environmental Data by Dennis R. Helsel 2005 • 250 pages • $115.95 + shipping Texas residents please add 6.75 % sales tax