7 Quality Control Tools Old and New

7 QC Tools which originated in Japan were primarily used for "Shop Floor" (factory) quality improvements by workmen formed and empowered groups called Quality circles. The old 7 QC Tools were:

Check Sheets - To collected data in a structured manner

Cause and Effect Diagram - To organize probable causes (used along with 5 Why technique)

Scatter Diagram - To visually display cause / effect relationship with data (correlation)

Pareto - Helps prioritize the key problems (based on problem/defect categories - Define Phase) or Key Causes (out of a list of causes - Analyze phase)

Histogram - To visually present distribution of data (displays process variation and can be compared with specification limits)

Control chart - To monitor process performance through time (can be used before and/or after an improvement project) and highlight "out of control" situations needing action

Stratification - Segment / segregate data based on input sources that may be contrbuting to it (for eg., vendor wise, equipment wise, team wise etc.,)


As the knowledge age dawned, organizations had to confront with problems and improvement challenges in transactional, office, planning and managerial tasks as well. Towards facilitating structured improvement in these areas, the NEW 7 QC got evolved. These were called NEW 7 QC Tools namely:

1. Affinity diagram: organizes a large number of ideas into their natural relationships.

2. Relations diagram: shows cause-and-effect relationships and helps analyze links between different aspects of a complex situation.

3. Tree diagram: Breaks down broad categories into lower level detail, helping to get the thinking much more specific

4. Matrix diagram: Helps to show relationship between multiple groups of information including strength of relationship

5. Matrix data analysis: Technique for analyzing and prioritizing select options among many available options.Uses defined criteria to arrive at prioritization

6. Arrow diagram: A Project Planning tool (a la PERT/CPM)

7. Process decision program chart (PDPC): To identify potential deviations w.r.t to identified plans