Chapter 2

Summarizing Quantitative Data: Means, Medians, and More

IN THIS CHAPTER

Bullet Calculating measures for center and spread

Bullet Interpreting your results properly

Bullet Compiling the results for a data discussion

Before data are organized in a chart or graph, the first step is to summarize them — that is, find a few numbers and/or words that can tell the story of the data in a nutshell. For quantitative data, the most important characteristics are the shape of the data (which you see in Chapter 4), where the center is located, and how much variability or spread is in the data. You may also want to point out any outliers in the data (numbers that appear far from the rest). And like everything else in statistics, there’s room for people to stretch the truth in how they choose to summarize their data (or in what they choose not to tell you). So it’s good to know the big ideas of how data are summarized and what to look for in terms of interpreting and evaluating data summaries. That’s what you practice in this chapter.

Finding and Interpreting Measures of Center

The most common way to summarize quantitative data is to describe where the center is. One way of thinking about what center means ...

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