CHAPTER 12

Inference for Means and Proportions

IN THIS CHAPTER

Summary: In the last chapter, we concentrated on estimating, using a confidence interval, the value of a
population parameter or the difference between two population parameters. In this chapter, we test to see
whether some specific hypothesized value of a population parameter, or the difference between two
populations parameters, is likely or not. We form hypotheses and test to determine the probability of
getting a particular finding if the null hypothesis is true. We then make decisions about our hypothesis
based on that probability.

Key Ideas

The Logic   of  Hypothesis  Testing

z   -Procedures versus  t   -Procedures

Inference   for a   Population  Mean

Inference   for the Difference  between Two Population  Means

Inference   for a   Population  Proportion

Inference   for the Difference  between Two Population  Proportions

We began our study of inference in the previous chapter by using confidence intervals to estimate
population values. We estimated a single population mean and a single population proportion as well as
the difference between two population means and between two population proportions. We discussed z-
and t -procedures for estimating a population mean. In this chapter, we build on those techniques to
evaluate claims about population values.