ABSTRACT
How do two or more variables relate to each other? Chapter 6 presents analyses of the relationship between two categorical variables. Here focus on the relationship between continuous variables: As the values of one variable increase, the values of the other variable tend to either systematically increase (+ relationship) or systematically decrease (- relationship). Positive and negative relationships can have the same magnitude, such as for linear relationships, assessed by the correlation coefficient. The sign of + or - indicates the direction of the relationship. The size of the coefficient indicates magnitude. The essential visualization for the relationship between two continuous variables is the scatterplot. The paired data values for each observation plot as a single point. Define the two coordinates of each point as the values of both variables for the corresponding observation.
