Lesson 5: Relationships Between Measurement Variables

Lesson Overview Section

In this lesson, we will examine the relationship between measurement variables; how to picture them in scatterplots and understand what those pictures are telling us. The overall goal is to examine whether or not there is a relationship (association) between the variables plotted. In Lesson 6, we will discuss the relationship between different categorical variables.

This chart shows us what kind of graphs we can use for two different variables of the same type. If both variables are categorical, the cluster bar graph is appropriate. For two measurement variables, we can use scatterplot.

Figure 5.1 Variable Types and Related Graphs

Objectives

After successfully completing this lesson you should be able to:

  • Explain the major features of correlation.
  • Identify the key features of a regression line.
  • Apply what it means to be statistically significant.
  • Find the predicted value of y for given choice of x on a regression equation plot.
  • Critique evidence for the strength of an association in observational studies.