Chapter 15

Correlation: The Rise and Fall of Relationships


check Understanding what correlation is all about

check Discovering how correlation connects to regression

check Drawing conclusions from correlations

check Analyzing items

In Chapter 14, I introduce the concepts of regression, a tool for summarizing and testing 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 employee aptitude and performance 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 Chapter 14, and you’ll see how those connections work. I also show you how to test hypotheses about relationships and how to use R functions for correlation.

Scatter plots Again

A scatter plot is a graphical way of showing a relationship between two variables. In Chapter 14, I show you a scatter plot of the data for employees at FarMisht Consulting, Inc. I reproduce that scatter plot here as Figure 15-1. Each point represents one employee’s ...

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