Pareto chart
Overview
The Pareto chart is also called 80/20 rule curve or "ABC".
What is the Pareto chart?
The Pareto chart is a chart with columns which presents the information in descending order and thus the out or the most important elements that explain a phenomenon or a situation.
In other words, the Pareto chart shows the most important causes which have produced the largest number of effects. Knowing that 20% of cases are causing 80% of the consequences.
This simple method, allows clear and efficient decision making by the group.
How to use the Pareto chart?
The Pareto chart is developed in several stages:
-
Identify the problem to solve.
-
To collect data (eg using the data collection) or use existing data.
-
Classify data into categories and provide a category "Miscellaneous" for categories with few items.
-
Quantify the importance of each category and determine the percentage of each compared to the total.
-
Classify the percentage decreasing value, the category "Miscellaneous" is still in last place.
-
Represent the data as a histogram.
The histogram can be complemented by "The curve of cumulative values" whose points are determined by adding the values of all categories (or causes) identified earlier, until 100%.
The curve "ABC", it splits the Pareto curve into three segments A, B and C:
- "A" represents 75 to 80% of all
- "A" + "B" represents 90 to 95% of all
- A + B + "C" represents 100% of all
Thus, when the causes for the segment "A" are treated, 75 to 80% of problems are eliminated. With this tool, the priorities for action are quickly displayed.
Example Pareto chart
In a company of canned fish, we want to solve the problem of post boxes bulged after sterilization. After research, a list of possible causes has been established and a sheet of data collection was completed.
The data are classified by category and decreasing order. It also calculates the percentage and accumulation.
|
Causes |
Number of times | % | Accumulation |
|---|---|---|---|
| Pressure of compressed air inadequate | 22 times | 44% | 44% |
| Overfilling boxes | 19 times | 38% | 82% |
| Leak at the drain | 5 times | 10% | 92% |
| Compressor failure | 2 times | 4% | 96% |
| Miscellaneous | 2 times | 4% | 100% |
|
Total |
50 times | 100% |
The Pareto chart for this example is as follows:
It noted that 82% of the problem comes from the pressure of the air and the overfilling of boxes.
You can also make other Pareto diagrams to solve the problem of filling the boxes and the lack of pressure of compressed air.