QUALITY TOOLS

QUALITY TOOLS

1. PARETO DIAGRAM

   • WHAT IS IT? The Pareto chart is a type of statistical graph in which a set of data is represented with bars in descending order. Also, in a Pareto chart, cumulative percentages are graphically shown using a frequency polygon. It’s a very common graph used in quality, but also in any other area that uses statistics.
     • H OW TO MAKE ONE? The steps to make a Pareto chart are: 1- Collect the statistical data of the problem to be analyzed. 2- Arrange the values according to their absolute frequency in descending order, that is, from highest absolute frequency to lowest. 3- Calculate the percentage of each category. To do this, simply divide the absolute frequency of the category by the total number of data points and then multiply by 100. 4- Determine the cumulative percentage, which is equivalent to the sum of the percentage of the category plus all the previous percentages. 5- Represent on a chart the absolute frequencies using bars and the cumulative percentages using a frequency polygon.
       • WHAT IS IT FOR? Mainly, Pareto diagrams are used to find the reason behind a problem and how important each possible cause is in relation to the whole. The Pareto diagram comes from the Pareto principle (or Pareto law), which says that 80% of the consequences come from 20% of the causes, or in other words, 80% of the results come from 20% of the activities.
         • E X AMPLE For a statistical study on computer sales, a sample of 50 people was asked what the main reason is for buying a computer, and the results have been recorded in the following data table

2. HISTOGRAM

   • WHAT IS!? A histogram is a graphical representation that organizes a group of data points into userspecified ranges, often called "bins" or intervals. It looks very similar to a bar chart, but it´s used specifically for continuous quantitative data
     • WHAT IS IT USED FOR?It lets you instantly see the shape of your data distribution (whether it is symmetrical, skewed to the left or right, or uniform). Identifying Patterns: It helps spot outliers, concentrations of data, or central tendencies at a glance. Quality Control: Commonly used in statistics and manufacturing to check if a process is performing within acceptable limits
       • ELEMENTS AND STRUCTURE Collect the data. 2. Arrange the data from lowest to highest. 3. Identify the minimum and maximum values. 4. Calculate the range. 5. Determine the intervals. 6. Create a frequency table. 7. Place the intervals and frequencies on the axes. 8. Draw the bars. 9. Add the title and axis labels

3. POKA YOKE

   • WHAT IS ?
     • Poka-Yoke is a tool used in quality management to prevent errors in production or work processes. The name comes from Japanese: “poka” means mistake or error, and “yoke” means to avoid. Therefore, Poka-Yoke can be understood as “mistake-proofing” or “error-proofing.” The main objective of Poka-Yoke is to prevent a person from making a mistake or to detect the mistake immediately, before it causes a defective product, an accident, or a problem in the process.
       • Characteristics of Poka - Yoke
         • The main characteristics are: * Prevents errors: It tries to stop mistakes before they happen. * Detects errors quickly: When an error cannot be prevented, it identifies it immediately. * It is simple: It usually uses mechanisms that are easy to understand. * It can be used in different processes: It can be applied in factories, offices, schools, services, and everyday activities. * Reduces defective products: It helps improve quality. * Can use technology: For example, sensors, alarms, or automatic systems. * Makes work easier: It helps workers perform activities correctly. * Focuses on the causes of errors: It tries to prevent the problem instead of only correcting the product afterward. * Helps standardize processes: It establishes a safer and more correct way to perform an activity
           • Advantages
             • 1. Reduces human errors because the process helps prevent mistakes. 2. Improves product and service quality. 3. Reduces waste because fewer defective products are produced. 4. Reduces costs by decreasing repairs, returns, and rework. 5. Saves time because problems can be detected quickly. 6. Improves safety in some processes. 7. Makes workers’ activities easier, especially in repetitive processes. 8. Increases efficiency by reducing interruptions and errors. 9. Helps maintain standardized processes. 10. Supports continuous improvement in a company.
               • Disadvantages
                 • 1. It can have an initial cost, especially when sensors or equipment are needed. 2. It requires time for design and installation. 3. Some mechanisms require maintenance. 4. If it is designed incorrectly, it can make the process more difficult. 5. Workers can become too dependent on the mechanism. 6. Not all errors can be eliminated, especially unpredictable situations. 7. In some cases, workers need training to use the system correctly.

4. QUALITY CIRCLES

   • WHAT IS?
     • They are small groups of workers who meet regularly to identify, analyze, and solve problems related to their work. Their purpose is to suggest improvements, increase quality, improve processes, and promote teamwork within an organization.
       • CHARACTERISTICS
         • Voluntary participation: Workers join the group because they want to participate. Small groups: Usually, a small number of workers from the same area participate. Regular meetings: They meet regularly to discuss problems and progress. Teamwork: Everyone shares ideas and opinions to find solutions. Problem solving: They identify work problems and look for ways to solve them. Continuous improvement: They always try to improve processes, quality, and productivity.
           • ADVANTAGES
             • 1. Shows the critical path It shows which tasks cannot be delayed, because if they are delayed, the entire project is delayed. 2. Calculates time realistically It uses 3 times: Optimistic, Most Likely, and Pessimistic time to get a more accurate estimate. 3. Helps prevent delays You can move resources from non-critical tasks to critical ones to avoid bottlenecks.
               • DISADVANTAGES
                 • 1. It is complex to create If the project has many tasks, the diagram becomes very large, confusing, and takes a long time to build. 2. It depends on estimates that can fail Since it uses 3 times (optimistic, likely, pessimistic), if those estimates are wrong, the entire calculation is wrong. 3. It is not very flexible if there are changes If tasks or the order change in the middle of the project, you have to redo almost the entire diagram.

5. DEMING CYCLE

   • WHAT IS THE DEMING CYCLE
     • The Deming Cycle (PDCA) is a method for continuous improvement in processes and quality. Plan: Identify the problem and make a plan. Do: Put the plan into action. Check: Review the results. Act: Make improvements based on the results.
       • DISADVANTAGES
         • It Takes Time Requires Commitment Completing the four phases can be slow, especially when a test needs weeks to show results. It is not the best option for urgent problems that need an immediate solution
           • WHO IMPLEMENTED IT?
             • The cycle was created by Walter A. Shewhart, who introduced the first ideas of the cycle in 1939. Later, W. Edwards Deming helped spread and develop the method, especially in Japan. Because of this, it became known as the Deming Cycle. Today, the cycle enjoys widespread recognition in the business and academic sectors worldwide. International standards such as ISO 9001 and 14001 (quality management systems and environmental management systems) include it as part of the implementation, maintenance, and improvement framework.
               • ADVANTAGES
                 • Continuous Improvement Decisions Based on Data Simple and Flexible Each cycle builds on the previous one, so processes keep getting better over time. Small and constant improvements add up to big results in quality and efficiency. Changes are tested on a small scale and measured before being adopted, which reduces risks and costs. Decisions are made with real results, not with opinions or assumptions. Its four steps are easy to understand and can be used in any process or industry. It also promotes teamwork, since everyone takes part in planning, testing, and learning.