A parallel plot is one of the few types of coordinate plots that show any number of variables in one plot. However, the relationships between variables might be evident only in the following circumstances:
Note: If the columns in a parallel plot use the Spec Limits column property, the specification limits appear as red lines.
To help you interpret parallel plots, compare the parallel plot with a scatterplot. In each of the following figures, the parallel plot appears on the left, and the scatterplot appears on the right.
The following relationship shows a strong positive correlation. Notice the coherence of the lines in the parallel plot.
Now, consider a case that encompasses both situations: two groups, both strongly collinear. One has a positive slope, the other has a negative slope. In Collinear Groups: Parallel Plot and Scatterplot, the positively sloped group is highlighted.
Finally, consider the case of a single outlier. The parallel plot shows a general coherence among the lines, with a noticeable exception.