Estimation of distributional parameters for censored trace level water quality data. 2. Verification and applications

Journal Article · Fri Jan 31 23:00:00 EST 1986 · Water Resour. Res.; (United States)

DOI:https://doi.org/10.1029/WR022i002p00147· OSTI ID:5464266

Helsel, D R; Gilliom, R J

Estimates of distributional parameters (mean, standard deviation, median, interquartile range) are often desired for data sets containing censored observations. Eight methods for estimating these parameters have been evaluated by R. J. Gilliom and D. R. Helsel (this issue) using Monte Carlo simulations. To verify those findings, the same methods are now applied to actual water quality data. The best method (lowest root-mean-squared error (rmse)) over all parameters, sample sizes, and censoring levels is log probability regression (LR), the method found best in the Monte Carlo simulations. Best methods for estimating moment or percentile parameters separately are also identical to the simulations. Reliability of these estimates can be expressed as confidence intervals using rmse and bias values taken from the simulation results. Finally, a new simulation study shows that best methods for estimating uncensored sample statistics from censored data sets are identical to those for estimating population parameters. Thus this study and the companion study by Gilliom and Helsel form the basis for making the best possible estimates of either population parameters or sample statistics from censored water quality data, and for assessments of their reliability.

• Research Organization: Geological Survey, Reston, VA
• OSTI ID: 5464266
• Journal Information: Water Resour. Res.; (United States), Journal Name: Water Resour. Res.; (United States) Vol. 22:2; ISSN WRERA
• Country of Publication: United States
• Language: English

Related Subjects

520100* -- Environment
Aquatic-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
COMPUTERIZED SIMULATION
DATA
DATA ANALYSIS
ENVIRONMENTAL QUALITY
INFORMATION
MATHEMATICAL MODELS
MATHEMATICS
MONTE CARLO METHOD
NUMERICAL DATA
REGRESSION ANALYSIS
SIMULATION
STATISTICAL DATA
STATISTICAL MODELS
STATISTICS
VERIFICATION
WATER QUALITY