How to draw Pareto Chart

February 26th, 2008 | by admin |

Pareto chart was designed by Pareto who describes a 80-20 principle. 80% of problems are caused due to 20% of sources. So if we concentrate on this 20% of sources we can always get away with 80% of problems.

Pareto chart can be plotted with the problems in the x-axis and the frequency of occurrence in the y-axis. Let me give an example. Say in your project code review, you find out the following errors: My assumption here is a web based project like Java or .Net technologies. You find out that these are the top four frequently occurred error during the code review. Now let us plot the pareto chart that is found below:

Step 1: Draft the raw data as below

raw.gif

Step 2: Rearrange the raw data by their order of frequency as below. Also, calculate the percentage. For example, tab order not followed percentage is calculated by dividing 25 by cumulative total of frequency column.

dataa.gif

Step 3: Calculate the cumulative percentage for all the errors. Example, for memory not freed error, cumulative percentage will be sum of 41.67% and 30%.

dataa2.gif

Step 4: Draw pareto chart as explained below. Pareto chart can be drawn by using combination chart. To make a combination column-line chart, select a standard clustered column chart in the first step of the Chart Wizard. Press the Finish button to skip through the rest of the Wizard, to generate the bar chart. To create a line chart showing the percentage, create another series and set the data values. If you want to combine the bar (Pareto) chart with a series graphed as a line, just graph both series as bars and then right click on the data series that you want as a line and select “Chart Type” and change it to a line.

pareto.gif

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