Sunday, 23 December 2018

How to make Pareto diagram?

Pareto diagram is one of the tools (tool) from the QC 7 Tools that are used frequently in regard to quality control. Basically, the Pareto diagram is a bar graph that shows the problem based on the large number of sequences of events. The sequence starts from the number of problems that most to least happened. In the graph, shown with the highest graphics (far left) to the lowest graph (far right).

In its application, the Pareto diagram or Pareto often referred to with this Chart is extremely useful in determining and identifying the priority issues that will be resolved. The problem most frequently occurs and is a top priority for us to take action.

Before you create a Pareto Diagram, data-related issues or events that we want to the analysis should be collected in advance. In General, a tool that is often used for the collection of data is to use a Check Sheet or Sheets check.

A Pareto diagram has the following objectives: 

  • Separate the few major problems from the many possible problems so you can focus your improvement efforts.

  • Arrange data according to priority or importance.

  • Determine which problems are most important using data, not perceptions.

How to Create a Pareto diagram?

The steps in making a Pareto Diagram is as follows:

  1. Identify issues that will be examined and the causes of the incident.
    (An example of the problem: high rates of Defects in production of PCB Assembly, Cause: Short Solder, No Solder, Missing Solder, Solder Ball and Crack)

  2. Determine the period of time required for analysis (e.g. per monthly, weekly or daily per)

  3. Make a note the frequency of the incident on the sheet check (check sheet)

  4. Make a list of the issue in accordance with the order of frequency of occurrence (from highest to lowest).

  5. Calculate the cumulative Frequency and Cumulative Percentage

  6. To draw a Frequency in the form of a bar graph

  7. To draw a cumulative Percentage in the form of line graph

  8. Translate the Pareto diagram

  9. Take action based on the priority of the incident/problem

  10. Repeat the above steps again implement the improvement actions (action improved) to do the comparison results.

A Pareto diagram is a graphical representation that displays data in order of priority. It can be a powerful tool for identifying the relative importance of causes, most of which arise from only a few of the processes, hence the 80:20 rule. Pareto Analysis is used to focus problem solving activities, so that areas creating most of the issues and difficulties are addressed first.

Following procedure will be useful to use Pareto diagram and its analysis:

  • The categories of group items.

  • Approximate measurement (frequency, quantity, cost, or time)

  • Decide the time period to gather data and use in the Pareto diagram (one work cycle, one full day, or one week)

  • Collect data, record and assemble data for the category each time.

  • Subtotal the measurements for each category.

  • Determine the appropriate scale for the measurements data collect.

  • Mark the scale on the left side of the chart.

  • Construct and label bars for each category by placing the tallest to the left, next tallest to its right and so on

  • Calculate the percentage for each category.

  • Draw a right vertical axis and label it with percentage in a graph paper. Be sure that left measurement corresponds to one-half and it should be exactly opposite 50% on the right scale.

  • Calculate and draw cumulative sums.

  • Add the subtotals for the first category and second category and place a dot above the second bar indicating the sum, then add subtotal of third category to the sum and place a dot above the third bar indicating the new sum and so on. Continue the adding subtotals and placing dots for all bars.

  • Connect the dots, starting from the top of first bar. The last dot should reach 100 percent on the right side.

In this way we can visualize the most important factors among a typically large set of factors through the Pareto diagram. A Pareto diagram often represents the most common sources of defects. The highest occurring type of defect, or the most frequent reasons for problems.

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