Chapter 5

Means, Medians, and More

In This Chapter

arrow Summarizing numerical data effectively

arrow Looking at means, medians, and standard deviation

arrow Working with percentages

In Chapter 4, you see a few statistics used to tell the story of data that falls into specific categories. The topic of descriptive statistics continues in this chapter, in which you focus on ways to summarize numerical data.

Measuring the Center with Mean and Median

With numerical data, measurable characteristics such as height, weight, IQ, age, or income are represented by numbers that make sense within the context of the problem (for example in units of feet, dollars, or people). Because the data have numerical meaning, you can summarize them in more ways than is possible with categorical data. The most common way to summarize a numerical data set is to describe where the center is. One way of thinking about what the center of a data set means is to ask, “What’s a typical value?” Or, “Where is the middle of the data?” The center of a data set can actually be measured in different ways, and the method chosen can greatly influence the conclusions people make about the data. This section hits on measures of center. ...

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