What are Seven QC Tools & How to Remember them?

    Amrendra Roy

    Understanding and using hard-core statistics for continuous improvement is an issue with the shop-floor people. In order to overcome this issue it was felt necessary to present statistics in graphical forms so that everyone can understand it.

    The 7QC tools made the quality control more simpler so that it could be comprehended easily by all. Now statistics is not a prerogative of some experts in the company. It could easily be percolated down the ranks, irrespective whether someone has a statistical background or not.

    7QC tools is a collection of statistical tools which need not to be applied in a particular sequence. However, to understand and remember it we need to connect them with each other.

    1. Flow chart
    2. Cause & Effect diagram
    3. Control charts
    4. Check list
    5. Histogram
    6. Pareto Chart
    7. Scatter Plot

    One can easily remember the list by using following relationship between the above tools (you can develop some other relationship).


    If you want to remember 7QC tools then remember these sequence of events used in continuous improvement.

    For starting any continuous improvement program, the first step is about defining the problem (quality characteristic ‘Y’ to be addressed). Once we define the problem, we need to understand the process in-depth using Process Flow Diagram to find the problem areas and non-value adding steps.

    From the process flow diagram, find the probable sources of variations (X)  affecting the desired output (Y) using Cause & Effect Diagram.

    Once we have identified the probable cause (X), then start monitoring ‘X’ and ‘Y’ using proper Control Charts. This will drop some of the ‘X’s’ came from the cause and effect diagram. Make note of ‘X’ that really affects the ‘Y’.

    Once you have real ‘X’ that can affect ‘Y’ then prepare a plan for data collection using Check List to support the cause and effect relationship.

    Data thus collected using check list is then arranged in graphical form using Histogram to have a quantitative pictorial view of the effect of ‘X’.

    The bars of the histogram constructed above is then re-arranged in descending order to give Pareto Chart. This arranges the causes (X) in descending order of their effect on ‘Y’. Take the list of ‘X’ (usually top 3) having prominent effect on ‘Y’ for continuous improvement.

    Finally show a quantitative relationship between top three ‘X’ and ‘Y’ using Scatter Plot in laboratory or by collecting more data from the plant and propose the improvement strategy by providing best conditions for ‘X’ so that ‘Y’ remains within the desired limits.

    Related Blogs

    7QC Tools: Flow Chart, Know Your Process Thoroughly

    7QC Tools: Fish Bone or Ishikawa Diagram

    7QC Tools: How to Extract More Information from the Scatter Plot?

    7QC Tools: How to Draw a Scatter Plot?

    7QC Tools: Scatter Plot — Caution! Misuse of Statistics!

    7QC Tools: Scatter Plot

    7QC Tools — How to Prioritize Your Work Using Pareto Chart?

    7QC Tools — How to Interpret a Histogram?

    7QC Tools — How to Draw a Histogram?

    7QC Tools — Histogram of Continuous Data

    7QC Tools — Histogram of Discrete Data

    7QC tools — Check List

    Excellent Templates for 7QC tools from ASQ

    Kindly do provide feedback for continuous improvement

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