Cited by 3,495Statistical Distribution Estimation and ApplicationsStatistical Methods in EpidemiologyProbability and Statistical Research

Estimation of Average Concentration in the Presence of Nondetectable Values

Hornung, Richard W., Reed, Laurence D.·1990·Applied Occupational and Environmental Hygiene

Abstract

In the attempt to estimate the average concentration of a particular contaminant during some period of time, a certain proportion of the collected samples is often reported to be below the limit of detection. The statistical terminology for these results is known as censored data, i.e., nonzero values which cannot be measured but are known to be below some threshold. Samples taken over time are assumed to follow a lognormal distribution. Given this assumption, several techniques are presented for estimation of the average concentration from data containing nondetectable values. The techniques proposed include three methods of estimation with a left-censored lognormal distribution: a maximum likelihood statistical method and two methods involving the limit of detection. Each method is evaluated using computer simulation with respect to the bias associated with estimation of the mean and standard deviation. The maximum likelihood method was shown to produce unbiased estimates of both the mean and standard deviation under a variety of conditions. However, this method is somewhat complex and involves laborious calculations and use of tables. Two simpler alternatives involve the substitution of L/2 and a new proposal of L/2 for each nondetectable value, where L = the limit of detection. The new method was shown to provide more accurate estimation of the mean and standard deviation than the L/2 method when the data are not highly skewed. The L/2 method should be used when the data are highly skewed (geometric standard deviation [GSD] approximately 3.0 or greater)

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Crossref · 10.1080/1047322x.1990.10389587

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Authors
Hornung, R. W., & Reed, L. D.
Affiliations
National Institute for Occupational Safety and Health (US)
Venue
Applied Occupational and Environmental Hygiene
Published
1990-01
Volume
5
Issue
1
Pages
46-51
ISSN
  • 1047-322X (ISSN-L)
  • 1521-0898
OpenAlex
W2016709601
Cited by
3,495
References
7
Citations by year
2026: 234 · 2025: 251 · 2024: 241 · 2023: 236 · 2022: 239 · 2021: 235 · 2020: 229 · 2019: 172 · 2018: 184 · 2017: 144 · 2016: 133 · 2015: 132 · 2014: 134 · 2013: 103 · 2012: 84
FWCI
10.29
Type
journal article
Language
en
Open access
closed
Locations
Applied Occupational and Environmental Hygiene (publishedVersion)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Distribution Estimation and Applications
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Probability and Statistical Research
Keywords
censored data, detection limit, maximum likelihood estimation, geometric standard deviation, estimation bias, contaminant exposure, occupational exposure monitoring

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