Cause-and-effect (fishbone) diagram
Sort the possible causes of one problem into groups, so the team looks across the whole system first.
Model · Study sheet · Foundation
Investigate and prevent defects
Agree acceptance criteria and distinguish variation from a meaningful signal.
Understand
Control chart
Tell normal variation from a real signal over time, so you act on special causes and change the process for the rest.
Model · Study sheet · Foundation
Cost of quality
Compare the cost of preventing and detecting errors with the consequences of failures.
Reference · Guide · Foundation
Pareto chart
Rank the causes of a problem by count, so the team fixes first the vital few that produce most of the effect.
Model · Study sheet · Foundation
Plan–do–check–act (PDCA)
Improve a process or a deliverable in small, tested steps.
Model · Study sheet · Foundation
Quality assurance vs quality control
Keep four quality checks apart: process, deliverable, specification and real need.
Model · Study sheet · Foundation
Statistical process control
Distinguish routine process variation from signals that merit investigation.
Reference · Guide · Advanced
Calculate
Pareto counts and cumulative share
Rank recorded problem categories to focus investigation.
Tool · Calculator + guide · Applied
Defect density and removal efficiency
Track observed defects on a consistent measurement boundary.
Tool · Calculator + guide · Applied
Process capability: Cp and Cpk
Compare a stable process’s spread and centring with specification limits.
Tool · Calculator + guide · Advanced
Original sources
Plan–Do–Study–Act
Connect a small test with evidence and a deliberate learning decision.
Framework · Source pointer · Foundation
EFQM Model
Find an organisational assessment approach for improvement work.
Framework · Source pointer · Foundation