Process Improvement Tools and Techniques
Yellow Belt candidates need working familiarity with the core toolkit and, crucially, when each tool is appropriate. Process mapping shows the sequence of steps; a SIPOC gives a high-level view of Suppliers, Inputs, Process, Outputs, Customers. Value stream mapping adds flow and waste analysis. Spaghetti diagrams trace physical movement.
For root cause analysis, use 5 Whys (simple, fast, but can miss branching causes) and fishbone/Ishikawa diagrams (organise potential causes into categories such as People, Process, Equipment, Materials, Environment, Measurement). Pareto analysis applies the 80/20 idea to prioritise the few causes producing most of the effect. Check sheets and histograms describe data; run charts and control charts show behaviour over time and separate common from special cause variation. Scatter plots suggest relationships; FMEA ranks risks by severity, occurrence, and detection.
Traps: confusing a Pareto chart (ranked bars with cumulative line) with a histogram (distribution of a variable); using a control chart to find root cause (it detects, it does not explain); treating correlation as causation from a scatter plot. Also remember that a fishbone organises hypotheses, while data confirms them.
Rule of thumb: describe first (maps, checksheets, histograms), then diagnose (Pareto, fishbone, 5 Whys, scatter), then decide and monitor (control charts, FMEA). Match the tool to the question's verb: 'identify the biggest cause' points to Pareto; 'organise possible causes' points to fishbone; 'monitor stability' points to a control chart.