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  • Writer's pictureFahad Gohar


What are the 7 QC Tools?

The 7 QC tools as defined by the American Society for Quality (ASQ) and accepted throughout the quality engineering community include:

  1. Cause-and-Effect Diagrams / Fishbone Diagram

  2. Pareto charts

  3. Control Charts

  4. Scatter diagrams

  5. Histograms

  6. Flowcharts

  7. Checklists

Cause-and-effect diagrams

The first of the 7 QC tools is the Fishbone Diagram helps organize ideas and understand the relationship between potential causes and an effect or a problem by formatting, arranging and organizing potential causes into themes and sub-themes in preparation for a cause identification effort. It helps stimulate thinking when developing the list of the potential sources of a problem. It guides concrete action and tracks the potential causes during an investigation effort to determine whether the item significantly contributes to the problem or not.

Pareto Charts

The second of the 7 QC tools is the Pareto chart is used to prioritize the contributors which make the biggest impact on a problem, or which represents the largest areas of opportunity. A Pareto chart is a tool to focus attention on priorities while trying to make decisions. It is a good communication tool that describes the data in a simple and easy-to- read bar diagram. The chart helps to study and analyze the frequency or occurrences of an event in a process and identify the biggest contributors. These diagrams communicate the principle of 80:20. It states that 80% of an effect comes from 20% of the causes.

Control Chart

The third of the 7 QC tools is the control chart. The best tool to investigate variation in a process is a control chart. A control chart is often called a time series plot that is used to monitor a process over time. It is a plot of a process characteristic, usually through time with statistically determined limits. When used for process monitoring, it helps the user to determine the appropriate type of action to take on the process depending on a degree of variation in the process.

Scatter diagrams

The fourth of the 7 QC tools is the scatter diagram. The scatter diagram is also known as a scatter plot or a correlation graph. It helps visualize the relationship between two variables. The graph helps check for outliers too.


The fifth of the 7 QC tools is the histogram. A histogram is a pictorial representation of a set of data. The histogram is a bar graph that shows the frequency of values. It is created by grouping the measurements into ‘‘cells” or “bins.” Histograms are useful to understand the location, spread, and shape of the data. In addition, potential outliers or missing data can be seen.

Flow charts

The sixth of the 7 QC tools is the flow chart. A flow chart is a visual representation of a process that can illustrate:

  • What activities are completed, by whom, in what sequence

  • Hand-offs between departments or individuals

  • Internal and external operational boundaries


The last of the 7 QC tools is the checklist. The purpose of a checklist is to summarize, and in some cases; graphically depict a tally count of event occurrences. A checklist is used when users are interested in counting the number of occurrences of an event, such as defects or nonconformances. In many instances, a checklist will summarize countable data related to certain types of defects and will provide a rough graphical representation of where, in a part or process, defects occurred.

Article Credit: Master of Project Academy


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