Currently, the 3-D bar graph is used in countless computer programs, scientific journals and newspapers to display financial, medical and other information in which two variables lead to an outcome. Alvaro Muoz, PhD, a professor of epidemiology at the School of Public Health, has developed the new Diamond Graph, which corrects these errors and represents all the variables equally in a form that is easy to read. He believes the new graphing method could replace the traditional 3-D bar graph in software commonly used in business and science. Dr. Muoz and his colleagues described the Diamond Graph method in an article published in the August 2003 edition of the peer reviewed journal, The American Statistician.

So what was wrong with the old method? According to Dr. Muoz, the 3-D bar graph has three main flaws. First, the variables, which equally contribute to an outcome, are not equally represented in the diagram. This gives the impression that one variable is more important than another. Second, it is sometimes difficult, if not impossible, to distinguish the true value of the bars, because of the problems of representing a three-dimensional image on a two-dimensional page. Because of perspective, some bars appear to be of greater or lesser value when they are actually of equal value. The third drawback of the 3-D graph is that it cannot be used to present overlapping data. In some cases, parallel bars with higher values may obscure those with lower values making the graph useless.

"The inaccuracies of the traditional 3-D bar graph may seem trivial, but they can be significant when you're dealing with important information like predicting your risk for a heart attack or plotting the performanc
'"/>

Contact: Tim Parsons or Kenna Brigham
paffairs@jhsph.edu
410-955-6878
Johns Hopkins University Bloomberg School of Public Health
12-Aug-2003