Sampling Design

Precision of the abundance estimate in a multiple-sample CMR study will be influenced by 3 factors:

• Abundance (N)

• Capture probability on each occasion (p)

• Number of capture occasions (k)

Of these, k and sometimes p will be under the control of the investigator, whereas we cannot control N but should have a general idea of its values (e.g., is it closer to 1000 , 10, or 100?).

Given guesses (or estimates from a pilot study) of N and p, we can derive estimates of the expected variance and thus relative precision (cv = sd/mean) that will be produced from different values of k. I have written a user-defined function in R to perform these calculations, and used it to produce plots of cv vs k for different combinations of N and p.  For example, for N=100 and p=0.3 a plot over k=2, 3,4, 5 provides:

R code to provide the above computations and various plots.