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Introduction to Inference

6

Introduction

Statistical inference draws conclusions about a population or process from sample data. It also provides a statement of how much confidence we can place in our conclusions. Although there are numerous methods for inference, there are only a few general types of statistical inference. This chapter introduces the two most common types: confidence intervals and tests of significance.

Because the underlying reasoning for these two types of inference remains the same across different settings, this chapter considers just one simple setting that is closely related to our study of the sampling distributions of in Section 5.2 (page 293): inference about the mean of a large population whose standard deviation is known. This setting, although unrealistic, allows us to focus on the underlying rationale of statistical inference rather than the calculations.

Later chapters present inference methods to use in most of the settings we met in learning to explore data. In fact, there are libraries—both of books and of computer software—full of more elaborate statistical techniques. Informed use of any of these methods, however, requires a firm understanding of the underlying reasoning. That is the goal of this chapter. A computer or calculator will do the arithmetic, but you must exercise sound judgment based on understanding.