We've come a long way in just short of 150 pages. We've carefully designed our study, collected our sample of data, and summarized it. The next step is learning about a broader population of interest from the sample. This is statistical inference—the process of using something we actually observe (the sample of data) to learn about something we do not (the entire population)—and it comes in two flavors: descriptive inference and causal inference.

This chapter begins our journey into the world of statistical inference. In what follows, we start with the logic of inference, illustrating how we use random samples from populations to answer research questions. Next, we develop the two different tools that analysts use to perform statistical inference: confidence intervals and hypothesis tests. To illustrate these ideas, we make generous use of examples throughout.

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