##
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 methods 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:

- Calculate the sample size needed for estimating population mean and population total,
- compute the confidence interval for population proportion,
- Given a desired level of confidence for estimating a population proportion, determine the sample size required using both the educated guess method and conservative method, and critically evaluate the advantages and disadvantages of both approaches,
- Determine the necessary sample size to estimate the population proportion, and
- Choose between using the educated guess method and the conservative method.