A Pareto Chart allows you to quickly identify the problem areas of your application by reporting those areas that have the greatest number of issues.  The philosophy of the Pareto Chart is based on the 80/20 rule – by identifying and fixing the larger areas first, the application can be stabilized a lot quicker.  Or, more specifically, correcting 20% of the currently known bugs will stabilize 80% of the application.

Using the data from our check sheet, we can produce the Pareto Chart below.  The chart has two graphs: 1) a bar graph that reports the measure of each area; and, 2) a line graph that shows the cumulative total of the issues.  The X axis reports the individual problem areas.  The Y axis on the left gives us a total bug count of each area.  Finally, the Y axis on the right reports the accumulative percentage of each of the areas.

Notice that the area that has the highest number of bugs is listed first and the remaining areas are listed in descending order.  Additionally, line graph increases by each area giving us a delta of the percentage of bugs that particular area represents.  The line graph should be arrive at 100% for the last problem area.


(click on image to enlarge)


From the chart above we can learn a few things.  From the check sheet, we already knew that JavaScript and misspelled words were our top two problem areas, but we now have a visual on the total impact of these two areas.  From a different perspective, we also see that bugs related to JavaScript are approximately 45% of our total bugs and misspelled words contribute another 35%.  The Pareto Chart above tells us that if we focus our QA efforts on just JavaScript and misspelled words alone, we would eliminate 80% of all of our current bugs.

Sample Reports

  1. Ishikawa (“fishbone”) Diagram
  2. Check Sheet
  3. Stratification (alternatively, flowchart or run chart)
  4. Control Chart
  5. Histogram
  6. Pareto Chart
  7. Scatter Diagram