Correlation measures both the strength and direction of the relationship between *x* and *y.* Figure 20.1 illustrates the different types of correlation in a series of scatter plots, which graphs each ordered pair of (*x,y*). The convention is to place the *x* variable on the horizontal axis and the *y* variable on the vertical axis.

Graph A in Figure 20.1 shows an example of positive linear correlation where, as *x* increases, *y* also tends to increase in a linear (straight line) fashion. Graph B shows a negative linear correlation where, as *x* increases, *y* tends to decrease linearly. Graph C ...

Start Free Trial

No credit card required