Chapter 11

# The t-Distribution

In This Chapter

Characteristics of the t-distribution

Relationship between Z- and t-distributions

Understanding and using the t-table

The t-distribution is one of the mainstays of data analysis. You may have heard of the “t-test” for example, which is often used to compare two groups in medical studies and scientific experiments.

This short chapter covers the basic characteristics and uses of the t-distribution. You find out how it compares to the normal distribution (more on that in Chapter 10) and how to use the t-table to find probabilities and percentiles.

## Basics of the t-Distribution

In this section, you get an overview of the t-distribution, its main characteristics, when it’s used, and how it’s related to the Z-distribution (see Chapter 10).

### Comparing the t- and Z-distributions

The normal distribution is that well-known bell-shaped distribution whose mean is μ and whose standard deviation is σ (see Chapter 10 for more on the normal distribution). The most commonly used normal distribution is the standard normal (also called the Z-distribution), whose mean is 0 and standard deviation is 1.

The t-distribution can be thought of as a cousin ...

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