Statistical Power of Presence‐Absence Data to Detect Population Declines

Statistical Power of Presence‐Absence Data to Detect Population Declines Abstract: Population declines may be inferred from a decrease in the number of sites at which a species is detected. Although such presence‐absence data often are interpreted informally, it is simple to test the statistical significance of changes in the number of sites occupied by a species. I used simulations to examine the statistical power (i.e., the probability of making the Type II error that no population decline has occurred when the population actually has declined) of presence‐absence designs. Most presence‐absence designs have low power to detect declines of <20–50% in populations but have adequate power to detect steeper declines. Power was greater if the population disappeared entirely from a subset of formerly occupied sites than if it declined evenly over its entire range. Power also rose with (1) increases in the number of sites surveyed; (2) increases in population density or sampling effort at a site; and (3) decreases in spatial variance in population density. Because of potential problems with bias and inadequate power, presence‐absence designs should be used and interpreted cautiously. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Conservation Biology Wiley

Statistical Power of Presence‐Absence Data to Detect Population Declines

Conservation Biology, Volume 13 (5) – Oct 23, 1999

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Publisher
Wiley
Copyright
Copyright © 1999 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0888-8892
eISSN
1523-1739
D.O.I.
10.1046/j.1523-1739.1999.98143.x
Publisher site
See Article on Publisher Site

Abstract

Abstract: Population declines may be inferred from a decrease in the number of sites at which a species is detected. Although such presence‐absence data often are interpreted informally, it is simple to test the statistical significance of changes in the number of sites occupied by a species. I used simulations to examine the statistical power (i.e., the probability of making the Type II error that no population decline has occurred when the population actually has declined) of presence‐absence designs. Most presence‐absence designs have low power to detect declines of <20–50% in populations but have adequate power to detect steeper declines. Power was greater if the population disappeared entirely from a subset of formerly occupied sites than if it declined evenly over its entire range. Power also rose with (1) increases in the number of sites surveyed; (2) increases in population density or sampling effort at a site; and (3) decreases in spatial variance in population density. Because of potential problems with bias and inadequate power, presence‐absence designs should be used and interpreted cautiously.

Journal

Conservation BiologyWiley

Published: Oct 23, 1999

References

  • Regional patterns of mussel species distributions in North American rivers.
    Vaughn, Vaughn

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