NADA Course Outline

Day 1
Types of Reporting Limits
• detection and quantitation limits
• implications for data analysis

Storing Nondetects in a Database
• three standard formats

Plotting Data with Nondetects
• censored boxplots
• censored probability plots
• scatterplots with nondetects
• survival curves

Overview: The Three Approaches
• ROS (probability plotting)
• maximum likelihood
• nonparametric methods
• why not to substitute (fabricate) data

Estimating Descriptive Statistics
• what's the mean of <1, 5 <10 and 17?
• parametric methods
• Kaplan-Meier and other nonparametric methods

Computing Interval Estimates
• how to compute confidence intervals with nondetects
• UCLs, UPLs, and UTLs for censored data
• bootstrapping with nondetects

Tests for paired data
• paired Prentice-Wilcoxon test
• paired “t-test” for censored data

Day 2
Comparing Two Groups
• Generalized Wilcoxon (nonparametric) test
• MLE “t-test”
• what to do with multiple reporting limits

Comparing Three or More Groups
• Generalized Wilcoxon (nonparametric) test
• MLE version of ANOVA
• familiar tests for one reporting limit

Correlation Methods
• censored correlation coefficients
• what to do when one or both have multiple detection limits?
• Kendall’s tau with one and more reporting limits
• likelihood correlation coefficient

Regression and Trends
• how to compute a line with nondetects?
• what to do with multiple reporting limits?
• Akritas-Theil-Sen line
• MLE for regression
• logistic regression

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