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CADDIS Volume 3

Conditional Probability Analysis: EPT Taxa Richness < 18 vs. Turbidity in Oregon Coastal Streams


  1. Analysis: Conditional probability analysis
  2. Independent variable: Turbidity (NTU)
  3. Dependent variable: Probability of unacceptable condition for EPA taxa richness at < 18
  4. Key: symbols = observations, solid line: nonlinear curve fit of logistic-like function with change in slope.
  5. Sample size: n = 49


  1. Conditional probability analysis does not produce model parameters. 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), Regional EMAP (REMAP)
  3. Project: REMAP Region 10 Washington/Oregon Coastal Streams and Yakima River Basin Streams Project
  4. Location: Washington & Oregon coastal and Yakima River Basin
  5. Environmental Monitoring and Assessment Program (EMAP) data and metadata.

Sampling Design

  1. Data collected 1994 through 1995.
  2. Chaloud, D.J. and D.V. Peck. 1994. Environmental Monitoring and Assessment Program - Surface Waters: Integrated Quality Assurance Project Plan for the Surface Waters Resource Group, 1994 Activities. EPA 600/X-91/080, Rev. 2.00. U.S. Environmental Protection Agency, Office of Research and Development, Las Vegas, NV 89193.
  3. Hayslip, G. A. (editor). 1993. EPA Region 10 In-stream Biological Monitoring Handbook (for wadeable streams in the Pacific Northwest). EPA-910/9-92-013. U. S. Environmental Protection Agency - Region 10, Environmental Services Division, Seattle, WA 98101.
  4. Catalog Documentation for REMAP Region 10. 1994-1995 Washington/Oregon Coastal Streams and Yakima River Basin Streams Project Data.


John F. Paul,, (919) 541-3160

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