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False Positive and Negative Charts
January 2006* to December 2011
The Branch of Quality Systems (BQS) operates an Organic Blind Sample Project (OBSP). One of the goals of the project is to document bias and variability for the National Water Quality Laboratory (NWQL) through the use of blind quality assurance (QA) samples. From these summaries, districts can be informed of the NWQL's performance on QA samples that parallel their own environmental samples.

The False Positive and False Negative charts provide result concentration and expected concentration respectively for every analyte for every method OBSP currently assesses. The charts exhibit a Reporting Level line. All data is provisional and may change if the OBSP deems necessary.

Note: If there are 20% or more false positives or false negatives, there may be a discussion in the OBSP Summaries (Internal access only) that may add to the interpretation of the data seen in these charts.

A red analyte name is an indication of a permanently estimated compound .
NOTE: Charts are presented as graphical images. Use the back button on your browser to return to analyte choices.

The charts and data that you might secure from this U.S. Geological Survey (USGS) web page (identified as "OBSP") have not received official USGS approval and as such are provisional and subject to revision. The charts and data are released on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use.


Click below for a scrollable list of analytes with false positives or negatives, sorted by NWQL parameter code

Lab Schedule 1383 - Semivolatile Compounds (base/neutral/acid - BNA), Whole Water Recoverable
Lab Schedule 1433 - Waste Water Compounds by GCMS, Filtered
Lab Schedule 2001 - Pesticides determinations by SPE and GCMS, Filtered
Lab Schedule 2021 - NAWQA 85 Volatile Organic Compounds by GCMS, Whole Water Recoverable
Lab Schedule 2033 - NAWQA ACT/ULUG Selected, Filtered Pesticides and Degradates (LS2003 plus 20 compounds)
Lab Schedule 2060 - Polar Pesticides and Metabolites by SPE and HPLC/MS, Filtered
Lab Schedule 2080 - Pharmaceuticals by HPLC-MS, Water, Filtered - custom, unapproved method
Lab Schedule 4024 - Gasoline Oxygenates, Un-acidified, Wat, Unfiltered
Lab Schedule 4433 - Waste Indicator Compounds, Unfiltered water, GCMS
Lab Schedule 4434 - Hormones in unfiltered water

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Questions/Comments?  dbeaty@usgs.gov