Chapter 8: Basic Quality Tools


This chapter will review the quality tools available that will improve manufacturing processes. It will also cover data collection rules and the importance of stratification.

7 Quality Tools

The following tools were first emphasized by Kaoru Ishikawa, in Tokyo. These tools are meant to improve the process and eventually through practice become an indispensable part of manufacturing (ASQ, 2022). Review the following slides and video to learn more about these quality tools.

Each of the quality tool titles are linked to more information, should you like to lean more about any of the tools.


Data Collection Rules

There are few rules to follow in regards to data collection during this process. Follow these rules when collecting data for your work.

  • No process without data collection
  • No data collection without analysis
  • No analysis without decision
  • No decision without action.
  • Additionally, planning of data collection needs to include a stratification plan

Before collecting data, ask yourself these questions:

  • How might the data need to be sorted, separated, or identified?
    • What is the product? (Including: part numbers, serial numbers, order numbers, etc.)
    • Who produced or measured?
    • When was it produced, including the time, shift, and day?
    • Where was it produced, including the plant, production line, machine numbers?
    • Include other important factors from the 4Ms and an E.
  • All of these factors should be captured with the data.

Importance of Stratification

Stratification sorts data, people, and objects into categories. This technique is used in conjunction with other data analysis tools. When different types of data have been collected together it can be difficult to sort through to find the meaning. Using stratification can identify patterns (ASQ, 2022).

This tool should be used before collecting data and when there are many sources of potential data. Some sources of data that might need to be stratified could be, but is not limited to: equipment, shifts, departments, materials, suppliers, products (ASQ, 2022).

Once the data is collected and is being plotted with a specific analysis tool, use a system to distinguish data between the sources. This could be coloration or symbols. Then, analyze the data separately, draw quadrants, count points, etc. to connect the similar data (ASQ, 2022). Review the video below to learn more about stratification.



American Society for Quality (2022). The 7 basic quality tools: Quality tools for process improvement. ASQ.

American Society for Quality (2022). What is stratification. ASQ.

CQE Academy, (2021, July 21). The 7 quality control (QC) tools explained [Video]. YouTube.

THORS elearning solutions (2022, February 25). What is stratification? [Video]. YouTube.


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SPC and Lean Manufacturing by Andrea Bearman and Roberta Gagnon is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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