In Section 12.1, we introduce capture-recapture sampling and discuss application of it to estimating population size. We then provide the formula for the variance of estimate. An example is provided for capture-recapture sampling. This is the direct sampling of capture-recapture where both the capture size and the second capture size are pre-determined.

In Section 12.2, we discuss inverse sampling for capture-recapture where the initial capture size is pre-determined but we sample until a fixed number of tagged items are recaptured. Here, the second capture size is random. An example is provided to compute the estimate as well as its estimated standard deviation.

In Section 12.3, the random response model is introduced to promote more truthful answers to senstive questions. An example is given to illustrate how to compute the estimate as well its estimated standard deviation.

**Lesson 12: Ch. 18.1 of ***Sampling* by Steven Thompson, 3rd edition

## Objectives

- use capture-recapture sampling method to estimate population size,
- distinguish between capture-recapture method and inverse capture-recapture method,
- use inverse capture-recapture sampling method to estimate population size, and
- use random response model to deal with sensitive questions.