Branch of Quality Systems
National Field Quality Assurance Program (NFQA)
The U.S. Geological Survey (USGS) began the National Field Quality Assurance Program in 1979. Since then more
than 100,000 reference have been distributed to about 150 USGS offices nationwide. The NFQA disburses about 6,500
proficiency samples annually for pH, specific conductance, and alkalinity to USGS, contract, and cooperator personnel.
Each field analyst receives 2 bottles of each type of proficiency samples they analyze. Today, the field-analyst
requests specific sample ranges that correspond to actual field values. The results from the program have been
summarized in bar charts (approximately 30K apiece) below.
Specific Conductance
pH
Alkalinity
The "fourth-spread statistic" displayed on the y-axis of each graph represents the data
range of the middle 50 percent of the values determined during each comparison.
Publications
OFR.92-163 -Summary of the U.S. Geological Survey National Field Quality Assurance Program from 1979 Through 1989
OFR.95-317 -Standard Procedures and Quality Control Practices for the U.S. Geological Survey National
Field Quality Assurance Program from 1982 Through 1993
OFR.96-130 -New Standard Operating Procedures and Quality Control Practices for the U.S. Geological
Survey National Field Quality Assurance Program Since January 1994
OFR.98-392 -Summary of the U.S. Geological Survey National Field Quality Assurance Program From 1979 Through 1997
The URL for this page is <http://nfqa.cr.usgs.gov/owqrlnfqa.html>.
If you have any questions or comments about this document, contact
Jonathan Currier.
Last modified: July 17, 2003
