Seven Quality Tools for Process Improvement

There are seven common Quality Tools you can use to understand and improve processes during a process improvement event.   Each tool helps you identify sources of variation and aids in the analysis, documentation, and organization of the information, which leads to process improvement. 

1. Flowcharts, or Process Maps, visually represent relationships among the activities and tasks that make up a process.   They are typically used at the beginning of a process improvement event; you describe process events, timing, and frequencies at the highest level and work downward.  At high levels, process maps help you understand process complexity.  At lower levels, they help you analyze and improve the process.
2. Ishikawa, Fishbone, or Cause & Effect Diagrams visually represent the causes of a problem – or effect – and help you determine the ultimate source of the problem — the root cause.  (This tool is called a “fishbone” diagram because of its appearance; Ishikawa was its inventor.)   The cause-and-effect diagram is used at the beginning of root cause analysis, to organize the causes of a problem (people, methods, equipment, materials, measurement, and environment) and prioritize them.
3. Data Checklists, check sheets, or recording tables are matrices designed to assist in the tallying, recording, and analysis of test results or event occurrences.  They are utilized in production to count defects and collect process data, which you analyze to identify opportunities for improvement.
4. The Pareto chart is named after Vilfredo Pareto, who came up with the Pareto Principle (or the “80/20 rule”), which says that 20% of the factors account for 80% of potential problems.  The Pareto chart ranks defects, causes, or data from the most significant to the least significant, in descending order.  Pareto charts help you separate the “vital few” from the “trivial many”.  They are typically used during process improvement analysis, to understand where to focus improvement for the greatest impact.
5. Histograms consist of vertical bars, side-by-side, that depict frequency distributions within tables of numbers and can help you understand data relationships over time (e.g., the familiar “bell curve”).  Histograms are generally used during process improvement analysis.
6. Scatter charts display relationships between dependent (predicted) and independent (prediction) variables.  They are used during hypothesis testing, to determine if there is a correlation between two variables and how strong the correlation is.  Less scattering indicates stronger correlation.
7. The control chart is a type of statistical process control tool.  Process performance is plotted over time against upper and lower control limits; this helps you readily identify process variations and enables determination of special cause and common cause variation.  Control charts are used during production, or after process improvement implementations, to ensure that processes are within control limits, or “in control”.

To achieve the best results, start by (1) drawing up a process map, so you understand the process flow.  Next, (2) analyze the process flows for the primary causes of problems and develop your cause-effect diagram.  Then, (3) collect data using check sheets and (4) plot your data using a Pareto chart and/or (5) a histogram.  Next, (6) determine the relationship of various variables in your cause-effect chain using a scatter chart.  Once you have solved your problem, (7) use a control chart to ensure that the process is staying within process control limits — demonstrate process control.

The Seven Quality Tools

To summarize, using these seven quality tools:

1. Flowcharts or Process Maps;
2. Ishikawa, Fishbone, or Cause & Effect Diagrams;
3. Data Checklists, check sheets, or recording tables;
4. Pareto Charts;
5. Histograms;
6. Scatter plots; and
7. Control Charts (SPC)…

…especially in combination, will help you improve your processes and achieve your objectives.

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Originally published in 2009 by Bizmanualz, Inc. under the title Seven Quality Tools for Process Improvement. All rights reserved. Reproduction permitted with attribution only. www.bizmanualz.com