On-Demand Webinars

HANDLING NONDETECT DATA CORRECTLY

Measurements of trace chemicals in environmental media (water, air, soils, biota) frequently result in values reported only as less than several laboratory reporting limits ("less-thans", "nondetects", or "qualified values"). Statisticians call these "censored data". Methods specifically designed for interpreting censored data, but rarely taught in classes on environmental statistics, can be used to compute summary statistics, perform hypothesis tests, and compute regression models.

Methods for fully extracting the information contained in data with nondetects will be introduced. The methods explicitly handle data with multiple detection limits. They can directly incorporate ‘qualified' values between detection and quantitation limits. Means and medians can be computed, hypotheses tests performed, and regression equations calculated without substituting any values for nondetects. This seminar introduces methods from the author's textbook Nondetects And Data Analysis: Statistics for censored environmental data, published in 2005 by John Wiley.

Webinar Objectives and Highlights:

• Methods for handling nondetect data without substituting numbers
• Handling ‘qualified' values between detection and reporting limits
• Software that performs methods for censored data
• Standard methods in other disciplines that could become standard in environmental applications

What You Will Learn:

• You will know of standard procedures for handling nondetect data without substituting values for them
• You will see how ‘qualified' values can be incorporated without just dropping the ‘E' or ‘J' qualifier and treating them as detected values
• You will see these methods performed with software
• You will know of methods for handling data with multiple detection limits that actually work well.

Whether you want to learn more about statistical methods or managing detection limits, this webinar will provide participants with information that is not available elsewhere on the web.