##
Overview
Section* *

Using the result of confidence intervals from the last lesson, this lesson starts with a discussion on selecting sample size for estimating the population mean as well as the population total by a confidence interval with a specified margin of error and specified level of confidence. In the second section, the confidence interval for estimating a population proportion is discussed. In the last section, sample sizes needed for estimating a population proportion are discussed. Both the educated guess and conservative method are introduced.

**Lesson 2: Ch. 4.1-4.2, 5.1-5.3, of ***Sampling *by Steven Thompson, 3rd edition.

## Objectives

Upon completion of this lesson, you should be able to:

- find the sample size needed for estimating population mean and population total
- know how to compute the confidence interval for population proportion
- find the sample size needed for estimating population proportion by both the educated guess method and conservative method
- find the sample size to estimate population proportion, and
- know when to use educated guess method and when to use conservative method