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Sample size formulae for estimating the true arithmetic or geometric mean of lognormal exposure distributions

Public Domain


Details

  • Personal Author:
    Hewett, Paul
  • Description:
    Simple formulas were developed to calculate the approximate size of sample needed to estimate either the true arithmetic or true geometric mean of a lognormal distribution to within a specified accuracy with a specified level of confidence. Such formulas could be used in prospective and cross sectional occupational health studies, and for developing an exposure database for studies on the effects of exposure on worker health. Computer simulation was used to validate the formulas. Results indicated that large sample sizes may be required if existing parameter estimates are derived from a limited number of prior measurements, or if the true exposure distribution has a large geometric standard deviation. The author suggests that reasonably accurate exposure data should be collected during the pilot study phase of a prospective study, as the accurate estimation of the true arithmetic mean or geometric mean of a single exposure group can require a sizable commitment in sampling resources. When the required accuracy is reduced, the size of the samples is also significantly lessened. To obtain an accuracy on the order of many medical measurements the sample sizes needed can be quite large. By performing a pilot study in which reasonably precise initial estimates of the distribution parameters for each exposure group are obtained, by grouping workers into exposure groups where the group geometric standard deviation is 2 or less, and by keeping the desired accuracy at a reasonable level, the total sample burden can be reduced. [Description provided by NIOSH]
  • Subjects:
  • Keywords:
  • ISSN:
    0002-8894
  • Document Type:
    Text
  • Genre:
    Journal Article
  • Place as Subject:
  • CIO:
    National Institute for Occupational Safety and Health (NIOSH)
  • Division:
    DRDS - Division of Respiratory Disease Studies
  • Topic:
    Workplace Safety & Health
  • Location:
    North America
  • Pages in Document:
    219-225
  • Volume:
    56
  • Issue:
    3
  • NIOSHTIC Number:
    nn:00225695
  • Citation:
    Am Ind Hyg Assoc J 1995 Mar; 56(3):219-225
  • Contact Point Address:
    Paul Hewett, National Institute for Occupational Safety and Health, 944 Chestnut Ridge Road, Morgantown, WV 26505
  • Federal Fiscal Year:
    1995
  • Peer Reviewed:
    True
  • Source Full Name:
    American Industrial Hygiene Association Journal
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:7a78149778b90440e03226f272729c30240bff072d983fa9efc10e7c0e6b2f40f2593ae6780f75f138446298826d330b4adaa4500dc3b1f4762cf97aa0204bdf
  • Download URL:
  • File Type:
    Filetype[PDF - 729.15 KB ]
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