The Pareto Principle Some Sample 80/20 Rule Applications 80% of process defects arise from 20% of the process issues. 20% of your sales force produces 80% of your company revenues. 80% of delays in schedule arise from 20% of the possible causes of the delays. 80% of customer complaints arise from 20% of your products or services. (The above examples are rough estimates.)

The Pareto Diagram Graph that ranks data classifications in descending order from left to right Pareto diagrams are used to identify the most important problems Advantage: Provide a visual impact of those vital few characteristics that need attention Resources are then directed to take the necessary corrective action

The Pareto Diagram Helps a team focus on causes that have the greatest impact Displays the relative importance of problems in a simple visual format Helps prevent “shifting the problem” where the solution removes some causes but worsens others

Constructing a Pareto Diagram Steps: Determine the method of classifying the data: by problem, cause, type of nonconformity, etc Decide if dollars (best), weighted frequency, or frequency is to be used to rank the characteristics Collect data for an appropriate time interval

Constructing a Pareto Diagram Steps cont’d: Summarize the data and rank order categories from largest to smallest Compute the cumulative percentage if it is to be used Construct the diagram and find the vital few

Pareto diagram 50% reduction Number of defects Percent of components 50% reduction Pareto diagram can be used to identify the degree of severity of quality problems. To eliminate defects and improve the operation, this tool can help us to make decision that which problems should be solved first.

Pareto diagram Before improvement After improvement

Pareto diagram No. of accidents

Questions อธิบายข้อเหมือนและข้อแตกต่างของ Histogram และ Pareto diagram

Cause-and-Effect Diagram It was developed by Dr. Kaoru Ishikawa in 1943 Picture composed of lines and symbols designed to represent a meaningful relationship between an effect and its causes Effect (characteristics that need improvement) on the right and causes on the left

Cause-and-Effect Diagram Enables a team to focus on the content of a problem, not on the history of the problem or differing personal interests of team members Creates a snapshot of collective knowledge and consensus of a team; builds support for solutions Focuses the team on causes, not symptoms Used to investigate either a “bad” effect and to take action to correct the causes or a “good” effect and to learn those causes responsible

Cause-and-Effect Diagram Advantages: Analyzing actual conditions for the purpose of product or service quality improvement Elimination of conditions causing nonconforming product or service and customer complaints Standardization of existing and proposed operations Education and training in decision-making

Cause-and-Effect Diagram Steps in the construction of a Cause-and-Effect Diagram: Identify the effect or quality problem Determine the major causes Determine all the minor causes. Request a brainstorming session Once the diagram is complete, evaluate it to determine the most likely causes Develop solutions

Cause-and-effect diagram Work methods (Man/Methods) Materials Quality characteristic (สิ่งที่ส่งผลกระทบต่อคุณภาพ และเป็นสิ่งที่ต้องการปรับปรุง) Equipment (Machine) Inspection (Measurement) cause effect

Cause-and-effect diagram Size 2.6 Worker Materials G axle bearing Wobble Inspection Tools

Cause-and-effect diagram (dispersion analysis)

Cause-and-effect diagram (process classification)

Cause-and-effect diagram (process classification) Cause-and-effect diagram shows that how scarring occurs during steel tubing process.

Good and poor cause-and-effect diagram B

Cause-and-effect diagram Cause-and-effect diagram with possible causes Is the cause-and-effect diagram good enough for solving the problem? How can we profoundly analyze and quantify the relationship between causes and effects?

Cause-and-effect diagram Cause-and-effect diagram after further study

Scattering diagram The result of investigating the conveyer speed (cause) and the severed length (effect) as shown above

Scattering diagram

Scattering diagram B C A Matching game D E

Previous 6 QC tools Static form of presentation Check sheet Histogram Pareto diagram Cause-and-effect diagram Scattering diagram Consolidate data, แสดงลักษณะภาพรวมของข้อมูลให้ชัดเจนและมีความหมายยิ่งขึ้น (เช่นรูปแบบการกระจายตัวของข้อมูล) Indicate problem areas, บ่งชี้ให้เห็นถึงลำดับความสำคัญของปัญหา Static form of presentation Show potential causes of defects affecting quality problem areas, แสดงให้เห็นถึงสาเหตุที่เป็นไปได้ของปัญหาที่มีผลต่อคุณภาพ แสดงข้อมูลในช่วงเวลาหนึ่งๆ ไม่แสดงการเปลี่ยนแปลงของค่ามูลตามช่วงเวลา หรือ ล๊อตการผลิต Show quantitative relationship between causes and defects, แสดงความสัมพันธ์ระหว่างตัวแปรที่เป็นสาเหตุและปัญหาที่มีผลต่อคุณภาพ

Control Chart day Static form Dynamic form

Control Chart day 3 3 Put the limit lines on the graph so that we can see if the data out of control or not!

Types of Control Chart ข้อมูลต่อเนื่อง เช่น หน่วยวัด ข้อมูลไม่ต่อเนื่อง เช่น จำนวนชิ้นส่วนที่เสีย ข้อมูลไม่ต่อเนื่อง ข้อมูลไม่ต่อเนื่อง เช่น จำนวนชิ้นส่วนที่เสียหาย จำนวนของที่เสีย สัดส่วนของเสียต่อล๊อต จำนวนรอยตำหนิ จำนวนรอยตำหนิต่อหน่วยชิ้นงาน

The Box Plot (or Box-and-Whisker Plot) Chapter 3 Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery. Copyright (c) 2009  John Wiley & Sons, Inc. 29

Copyright (c) 2009 John Wiley & Sons, Inc. Comparative Box Plots Chapter 3 Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery. Copyright (c) 2009  John Wiley & Sons, Inc. 30