New Zealand Journal of Ecology (2011) 35(2): 189- 190

Calculating the probability of absence using the Credible Interval Value

Short Communication
Graham B. McBride 1*
Peter Johnstone 2
  1. NIWA, PO Box 11 115, Hamilton 3216, New Zealand
  2. AgResearch, Invermay Agricultural Centre, Private Bag 50 034, Mosgiel 9053, New Zealand
*  Corresponding author

A common question that arises when considering the results from a well-designed sampling programme for a rare or invasive species is: ‘Sampling has failed to detect a species that could have been present, so can we calculate the probability that it truly was absent during the sampling period?’ Noting that this invokes a Bayesian view of ‘probability’, which therefore must be accepted if the question is to be answered in the affirmative, we present a method of addressing it.