Chapter 8

The t-Distribution

IN THIS CHAPTER

Understanding the basics of the t-distribution

Finding probabilities using the t-table

The t-distribution is a very commonly used distribution in data analysis. If you’ve heard of the t-test (and if you haven’t, you will), it’s the t-distribution that plays a big part. In this chapter, you find out how the t-distribution works, how to find probabilities for it, and how it relates to the Z-distribution (see Chapter 6).

Getting to Know the t-Distribution

The t-distribution is typically used to study the mean of a population. It is often used to estimate the population mean: for example, the average age of the people who buy a certain product, or the average price of gas in your hometown. It is also often used to test the reported value of a population mean: For example, someone may want to know whether the average age of people buying the product is higher this year than last year, or someone may report that the average price of gas is a certain value and you want to challenge, or test, this reported value.

The Z-distribution (discussed in Chapter 6) is also used to answer these kinds of questions, and in fact, the Z- and t-distributions can be thought of as cousins. The idea here is to sort out which particular role the t-distribution ...

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