Conditional Probability Analysis: Chlorophyll a > 30 vs. Total Phosphorus for Northeast Lakes

Plot

1. Analysis: Conditional probability analysis
2. Independent variable: Total phosphorus concentration in upper water column (ug/L)
3. Dependent variable: Probability of unacceptable condition for chlorophyll a at > 30 (ug/L)
4. Key: symbols = observations, dashed line = 95% Confidence Intervals
5. Sample size: n = 483

Model

1. Conditional probability analysis does not produce a model equation. Rather, it plots the probabilities of observing the stated impairment (i.e., item 3 in the list above) over a stressor intensity gradient.
2. Date: 8 November 2006

Data Analysis

1. Program: S-Plus Version 7.0, user written scripts, variable weighting for site data

Data Origin

1. Agency: U.S. Environmental Protection Agency
2. Program: Environmental Monitoring and Assessment Program (EMAP).
3. Project: Surface Waters, Northeast Lakes Data
4. Location: Northeast United States

Sampling Design

1. Data collected using the EMAP probability design over July through September in 1991 through 1994.
2. Single grab sample at 1.5 m below surface with van Dorn sampler according to Baker, JR, GD Merritt and DW Sutton (eds.). 1997. Environmental Monitoring and Assessment Program - Surface Waters: Field Operations Manual for Lakes.
3. Catalog Documentation for EMAP Surface Waters Northeast Lakes Data, EMAP.

Contact

John F. Paul, paul.john@epa.gov, (919) 541-3160