If you need to decide which issues you're going to deal with most urgently in the company you work for, the Pareto Diagram is the ideal tool for that! With it, you will be able to have more control over the nonconformities and thus increase the quality of the process.
What is the Pareto Diagram?
The Pareto Diagram is one of the main tools when it comes to quality in an Organization. The Pareto Principle, better known as Rule 20-80, tells us that 20% of the root causes account for 80% of the problems in an organization, that is, if we solve this 20 %, we end up with most of the problems.
To explain better, we created a very recurrent situation in our daily life: Loss of power in a car. Whenever this problem occurred, the mechanic would make a diagnosis in the car and find the cause for the problem. So, the table was created:
Sorting and Organizing Data
Therefore, every time you want to work with this tool, the first step is to collect the causes/defects and the frequencies that they have occurred in a certain period of time.
The second step is to place these frequencies in descending order. To do this, simply select any cell inside the table and click the Data> Sort.
The following panel will appear, in which you will sort in descending order the number of occurrences:
The result will be:
Now we have to identify two parameters: the percentage (%) that each occurrence obtained in the total and what is the accumulated frequency, given by the sum of the frequency of the defect with the previous one. In the case of the first data this sum does not occur. Let's see:
We use the function = SUM () to find the total number of occurrences. Therefore, we only divide the occurrence of each defect by the sum of the defects. Next, let's calculate the cumulative frequency:
Creating the graph
As explained above, simply add up the frequency of the defect and the previous one. Obligatory, the last data in the list has to appear 100.00%, since it shows that all data has been calculated.
With this data, just create the chart. To do this, we will click on an empty cell in the spreadsheet and insert a graphic of 2D Columns:
A "whiteboard" will appear, because our chart does not have data yet. So let's select it and click on the option: Select data.
When we click on this option, the table below will appear:
In the field of Subtitle Entries (Series) we will put the data present in the columns: Number of Occurrences and % Accumulated. To do this, click on Add:
In the name of the series we insert the cell with the name "number of occurrences" and in values of the series the interval referring to the number of occurrences of each defect. The result was:
We will do the same procedure for the % Accumulated series, getting the result:
Now we have to place the horizontal axis labels. To do this, we will use the Horizontal Axis Labels field (Categories). Let's select the data present in the field "defect types":
Configuring the Pareto Diagram
We can see that the % Accumulated series is on the Percentage scale and the series number of occurrences is in Number. So let's put the % Accumulated series on a secondary axis.
To do this, we will click on the bars of this series with the right mouse button and select the option: format data series> secondary axis.
Our graph will look like this:
We will change the chart type from the % Accumulated series to 2D Rows. So, just click on this series> Insert> Graphics> 2D Line> Line with Markers:
The result will be:
We can see that the main causes of the loss of power are the adulterated fuel and clogged nozzles. Therefore, stopping to refuel at gas stations that do not have quality seal can contribute to solving these two main problems.