Effect of censoring trace-level water-quality data on trend-detection capability

Journal Article · Sun Jul 01 00:00:00 EDT 1984 · Environ. Sci. Technol.; (United States)

DOI:https://doi.org/10.1021/es00125a009· OSTI ID:6452189

Gilliom, R J; Hirsch, R M; Gilroy, E J

Monte Carlo experiments were used to evaluate whether trace-level water-quality data that are routinely censored (not reported) contain valuable information for trend detection. Measurements are commonly censored if they fall below a level associated with some minimum acceptable level of reliability (detection limit). Trace-level organic data were simulated with best- and worst-case estimates of measurement uncertainty, various concentrations and degrees of linear trend, and different censoring rules. The resulting classes of data were subjected to a nonparametric statistical test for trend. For all classes of data evaluated, trends were most effectively detected in uncensored data as compared to censored data even when the data censored were highly reliable. Thus, censoring data at any concentration level may eliminate valuable information. Whether or not valuable information for trend analysis is, in fact, eliminated by censoring of actual rather than simulated data depends on whether the analytical process is in statistical control and bias is predictable for a particular type of chemical analyses.

• Research Organization: Geological Survey, Reston, VA
• OSTI ID: 6452189
• Journal Information: Environ. Sci. Technol.; (United States), Vol. 18:7
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ORGANIC COMPOUNDS
DETECTION
WATER QUALITY
DATA ANALYSIS
MEASURING METHODS
MONTE CARLO METHOD
RELIABILITY
SIMULATION
STATISTICAL DATA
TRACE AMOUNTS
WATER POLLUTION
DATA
ENVIRONMENTAL QUALITY
INFORMATION
NUMERICAL DATA
POLLUTION
520200* - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)