Estimates of wildlife population sizes are frequently constructed by combining counts of observed animals from a stratified survey of aerial sampling units with an estimated probability of detecting animals. Unlike traditional stratified survey designs, stratum-specific estimates of population size will be correlated if a common detection model is used to adjust counts for undetected animals in all strata. We illustrate this concept in the context of aerial surveys, considering 2 cases: 1) a single-detection parameter is estimated under the assumption of constant detection probabilities, and 2) a logistic-regression model is used to estimate heterogeneous detection probabilities. Naïve estimates of variance formed by summing stratum-specific estimates of variance may result in significant bias, particularly if there are a large number of strata, if detection probabilities are small, or if estimates of detection probabilities are imprecise.
How to translate text using browser tools
1 April 2008
Variance of Stratified Survey Estimators With Probability of Detection Adjustments
John Fieberg,
John Giudice
ACCESS THE FULL ARTICLE
It is not available for individual sale.
This article is only available to subscribers.
It is not available for individual sale.
It is not available for individual sale.
Journal of Wildlife Management
Vol. 72 • No. 3
April 2008
Vol. 72 • No. 3
April 2008
detection probability
double sampling
population estimate
sightability adjustment
Stratified random sampling
variance estimators