SPSS Statistics Workbook For Dummies

Chapter 10

Testing Relationships with Correlation

IN THIS CHAPTER

Viewing relationships with scatterplots

Assessing relationships with the Pearson correlation

A correlation studies the relationship between two continuous variables to determine whether one variable increases or decreases in relation to another variable. For example, you might study the relationship between the number of items purchased and the total amount spent, and find that as the number of items purchased increases, the amount spent increases. The variables are correlated with each other because changes in one variable affect the other.

The Pearson correlation coefficient measures the extent — the strength and direction — of the linear (straight-line) relationship between two continuous variables. For example, you might want to know whether higher SAT scores are associated with higher first-year college GPAs; or whether eating more often at fast-food restaurants is related to more frequent shopping at convenience stores; or whether lower levels of depression are associated with higher self-esteem scores.

In this chapter, you use a scatterplot to display the relationship between two continuous variables. You then use correlation to quantify this relationship.

Viewing Relationships

Graphs organize data and ...