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Poder Estadístico de la Presencia‐Ausencia de Datos para Detectar Disminuciones Poblacionales
Author(s) -
Strayer David L.
Publication year - 1999
Publication title -
conservation biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.2
H-Index - 222
eISSN - 1523-1739
pISSN - 0888-8892
DOI - 10.1046/j.1523-1739.1999.98143.x
Subject(s) - statistical power , population , statistics , population density , type i and type ii errors , range (aeronautics) , population decline , population size , sampling (signal processing) , demography , biology , geography , mathematics , computer science , computer vision , materials science , filter (signal processing) , sociology , composite material
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.