Chapter 15

Correlation: The Rise and Fall of Relationships

In This Chapter

arrow Understanding what correlation is all about

arrow Discovering how correlation connects to regression

arrow Drawing conclusions from correlations

arrow Analyzing items

In Chapter 14, I show you the ins and outs of regression, a tool for summarizing relationships between (and among) variables. In this chapter, I introduce you to the ups and downs of correlation, another tool for looking at relationships.

I use the example of SAT and GPA from Chapter 14, and show how to think about the data in a slightly different way. The new concepts connect to what I show you in the preceding chapter, and you’ll see how that works. I also show you how to test hypotheses about relationships and how to use Excel functions and data analysis tools for correlation.

Scatterplots Again

A scatterplot is a graphic way of showing a relationship between two variables. Figure 15-1 is a scatterplot that represents the GPAs and SAT scores of 20 students at the fictional Sahutsket University. The GPAs are on a 4.0 scale and the SATs are combined Verbal ...

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