Estimating the encounter rate variance in distance sampling

RM Fewster, Stephen Terrence Buckland, KP Burnham, David Louis Borchers, P E Jupp, JL Laake, Len Thomas

Research output: Contribution to journalArticlepeer-review

111 Citations (Scopus)

Abstract

The dominant source of variance in line transect sampling is usually the encounter rate variance. Systematic survey designs are often used to reduce the true ariability among different realizations of the design, but estimating the variance is difficult and estimators typically approximate the variance by treating the design as a simple random sample of lines. We explore the properties of different encounter rate variance estimators under random and systematic designs. We show that a design-based variance estimator improves upon the model-based estimator of Buckland et al. (2001, Introduction to Distance Sampling. Oxford: Oxford University Press, p. 79) when transects are positioned at random. However, if populations exhibit strong spatial trends, both estimators can have substantial positive bias under systematic designs. We show that poststratification is effective in reducing this bias.
Original languageEnglish
Pages (from-to)225-236
Number of pages12
JournalBiometrics
Volume65
Issue number1
DOIs
Publication statusPublished - Mar 2009

Keywords

  • Distance sampling
  • Encounter rate
  • Line transect sampling
  • Point transect sampling
  • Stratified variance estimators
  • Systematic sampling
  • Variance estimation

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