Basic Analysis and Graphing - SAS

148 Performing Oneway Analysis Chapter 5
Compare Means
Using Comparison Circles
Each multiple comparison test begins with a comparison circles plot, which is a visual representation of group
mean comparisons. Figure 5.11 shows the comparison circles for the All Pairs, Tukey HSD method. Other
comparison tests lengthen or shorten the radii of the circles.
Figure 5.11 Visual Comparison of Group Means
Compare each pair of group means visually by examining the intersection of the comparison circles. The
outside angle of intersection tells you whether the group means are significantly different. See Figure 5.12.
• Circles for means that are significantly different either do not intersect, or intersect slightly, so that the
outside angle of intersection is less than 90 degrees.
• If the circles intersect by an angle of more than 90 degrees, or if they are nested, the means are not
significantly different.
Figure 5.12 Angles of Intersection and Significance
angle greater
than 90 degrees
angle equal to
90 degrees
angle less than
90 degrees
not significantly
different
borderline
significantly
different
significantly
different
If the intersection angle is close to 90 degrees, you can verify whether the means are significantly different by
clicking on the comparison circle to select it. See Figure 5.13. To deselect circles, click in the white space
outside the circles.