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Factsheet – 7 Quality Control Tools

by Chris Cooley

Basic Quality Control Tools and techniques that are vital in the visualisation and understanding of a problem or situation by analysing the available data in the most effective way.

The 7 basic Quality Control tools are as follows;

  1. Pareto Charts
  2. Cause & Effect Diagrams
  3. Graphs & Control Charts
  4. Check Sheets
  5. Histograms
  6. Scatter Diagrams
  7. Stratification

1. Pareto Charts

A bar graph displaying data by importance i.e quantity
A Pareto provides a clear visual picture of data displayed by priority or contribution, showing exactly where to dig first.


  1. Separates the critical few from the trivial many
  2. Used to decide which part of the problem to tackle first
  3. Based on the Pareto principle (80 % of problems come from 20 % of causes)

2. Cause & Effect (Ishikawa or Fishbone) Diagram

A diagram showing all the factors which could potentially affect a problem or process
Brainstorming, is by definition is a fairly random process, and an Ishikawa or Fishbone diagram can provide a simple, visual and logical breakdown of the problem by grouping potential causes under one of 4 main headings;

  1. Machine
  2. Man
  3. Method
  4. Material

The diagram is built up around the central spine of the problem & the 4 main bones (headings) hence the widely used name ‘Fishbone’, clarifying and visualising the ideas into a more easily interpretable format.


  1. A tool for visualising & categorising a ‘brainstorming’ exercise
  2. Identify potential causes of a problem
  3. Breaks causes down into their smallest parts
  4. Shows how causes interact

3. Graphs & Control Charts

There are 4 main types of graph used to display general data;

Line or Run Chart: visualise a trend

Bar Graph: compare 2 or more values

Pie Chart: show relative magnitudes,frequencies or percentages

Radar: compare performance of different entities against common criteriaControl Charts: A continuous picture of a process and it’s variation

4. Check sheets

A simple document used for the collection of data in real time, at the point where the data is generated, by hand.


  1. Simple, hand completed
  2. In real time at the actual location

5. Histograms

A bar graph displaying a number of observations or measurements within a rangeA simple tool for showing the spread or distribution of a range of data & measuring how much variation exists. Very effective for showing what percentage of the outputs of a process are acceptable or should be rejected


  1. A picture of the distribution
  2. To look at patterns
  3. Compare distribution to specifications

6. Scatter diagrams

A scatter diagram is effectively a line graph with no lineUsed to study possible relationships between two variables. The purpose being to show what happens to one variable when another is changed


  1. The relationship between two variables
  2. What effect do changes have

7. Stratification

Analysing data which has been separated by different criteria

Typically data is analysed divided by the following criteria;

  1. By time (Month, day, shift, time etc)
  2. By Process (Machine, tool, jig, die etc)
  3. By Working Method (Temp, Pressure, speed etc)
  4. By Workforce (Shift, section, experience)
  5. By Product (Batch number, part number, supplier etc)

What these tools are for: Painting a picture by numbers

Data needs to be fully and clearly understood to ensure that the message it provides is clear and accurate. Ensuring that you look at the data from a number of different angles ensures you see the whole story. Think of the data as a three dimensional shape (like a rubik’s cube), which can look very different depending on where you view it from and by the criteria on which it’s judged.
The real power of charts and graphs is in the visualisation, painting an easily interpreted picture from the numbers, using the 7 Quality Control Tools will help you achieve a clear picture every time.

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