Papers in the Biological Sciences


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Published in Ecological Applications, 13(6), 2003, pp. 1790–1801. Copyright 2003 by the Ecological Society of America. Used by permission.


The use of presence/absence data in wildlife management and biological surveys is widespread. There is a growing interest in quantifying the sources of error associated with these data. We show that false-negative errors (failure to record a species when in fact it is present) can have a significant impact on statistical estimation of habitat models using simulated data. Then we introduce an extension of logistic modeling, the zero-inflated binomial (ZIB) model that permits the estimation of the rate of false-negative errors and the correction of estimates of the probability of occurrence for false-negative errors by using repeated visits to the same site. Our simulations show that even relatively low rates of false negatives bias statistical estimates of habitat effects. The method with three repeated visits eliminates the bias, but estimates are relatively imprecise. Six repeated visits improve precision of estimates to levels comparable to that achieved with conventional statistics in the absence of false-negative errors. In general, when error rates are ≤ 50% greater efficiency is gained by adding more sites, whereas when error rates are > 50% it is better to increase the number of repeated visits. We highlight the flexibility of the method with three case studies, clearly demonstrating the effect of false-negative errors for a range of commonly used survey methods.

Includes Supplement. Two downloadable program files described there are attached (below) as "additional files." (41 kB)
"Compiled" package ready for installation in R running under Microsoft Windows

obserr_0.3-1.tar.gz (6 kB)
"Source" package that requires the R source code development tools for installation, but can be installed in R under any operating system.

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