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.

  G1 31% 18% 64% 3% 12% 28% 21% 9% 6% 80% 37% 91% 2% 52% 47% P1 P2 P3 G2 G3 G4 G5 RELATIONSHIPS BETWEEN VARIABLES TWO CATEGORICAL VARIABLES TWO CATEGORICAL VARIABLES ONE MEASUREMENT ANDONE CATEGORICAL VARIABLE Bar graph of percents by groups Bar graph of proportions by groups Side-by-side Boxplot Scatterplot Table  

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.