Quantile Regression: EPT Taxa Richness vs. Metal Toxicity Units for Colorado Streams
- Analysis: Quantile regression
- Independent variable: Metal Toxicity Units
- Dependent variable: EPT taxa richness
- Key: dot=observation; line= 90th quantile
- Sample size: n = 37
- EPT taxa richness = 22.565 - 8.708*(Metals-Toxicity Units)
- Date: 12 November, 2006
|Variable||Estimate||Lower CL||Upper CL||Test Type||Statistic||p|
|Metal Toxicity Units||-8.708||-16.112||-1.303||T value||-2.387||0.022|
- Model generated using SAS Proc QUANTREG with the smoothing algorithm. The WALD and Likelihood test statistics were used to test the linear null hypothesis, H0: slope=0.
- Analysis for sites classified as pH neutral, but with strong AMD input.
- Metal Toxicity Units (TU) were calculated as sum of the ratios of each measured metal concentration with the criterion for that metal.
- Replicate visits to a site were not excluded from the data set.
- Agency: U.S. Environmental Protection Agency
- Program: Environmental Monitoring and Assessment Program (EMAP)
- Project: Colorado Metals Belt Stream Assessment (EPA Region 8)
- Filenames: Files benmet, fishmet and chem downloaded from the Surface Waters Information Management (S.W.I.M.S.) database web site
- Data collected 1994 through 1995.
- Analyzed metals and metalloids: aluminum, arsenic, cadmium, chromium, copper, iron, manganese, nickel, lead, selenium, silver, zinc.
- A description of the sampling methods may be found in the EMAP West Methods Manual for Streams found on the S.W.I.M.S. database web site.