Lean Six Sigma Yellow Belt Practice Questions

Using visual aids (like photos of the correct layout) and checklists are forms of Visual Controls. The checklists also serve as a tool for conducting regular 5S Audits. Both are crucial for the 'Sustain' phase of 5S to prevent the workspace from reverting to its previous state. Kanban is for inventory control, and Poka-Yoke is for error-proofing.

An X-Y Diagram, also known as a Cause and Effect Matrix, is a tool used to prioritize potential root causes (X's). It works by systematically evaluating the correlation between key process inputs (X's) and customer outputs (Y's). The team assigns numerical scores to these relationships, resulting in a ranked list of the most influential inputs to investigate further.

A Control Plan is a living document created during the Control phase that details how to maintain the gains from an improvement project. It specifies the key process variables to monitor, the methods and frequency of measurement, and, crucially, a Response Plan that outlines the specific actions to be taken if the process becomes unstable or goes out of control.

The business case provides the justification for undertaking the project. It links the project to the organization's strategic goals and explains, often in financial terms, why the project is a priority and what the expected return on investment will be. It answers the question, 'Why should we do this project?'

Cp measures the potential capability of the process, assuming it is perfectly centered. A Cp of 1.67 is very good, indicating the process spread is narrow compared to the tolerance width. Cpk measures the actual capability, taking the process centering into account. A very low Cpk (0.33) combined with a high Cp indicates that while the process is consistent (low variation), its mean (20.4mm) is significantly shifted away from the target (20.0mm), causing defects.

The waste of Motion refers to the unnecessary movement of people (e.g., walking, bending, reaching). In this scenario, the staff members walking to get forms is a classic example of wasted motion. Transportation refers to the unnecessary movement of materials or products, not people.

A Fishbone (or Ishikawa) Diagram is specifically designed for root cause analysis. It helps teams visually organize the potential causes of a problem (the effect) into logical categories (like Manpower, Method, Machine, etc.), which facilitates a structured brainstorming session. SIPOC defines process scope, Pareto prioritizes causes by frequency, and Control Charts monitor process stability over time.

This statement is false. A device that physically prevents an error from occurring is a 'prevention' or 'control' type of Poka-Yoke, which is the most effective form. A 'detection' type would allow the mistake to happen but would immediately signal an alarm or stop the line to alert the operator.

Internal Failure Costs are incurred to remedy defects discovered before the product or service is delivered to the customer. Since the incorrect invoices are being re-issued before being sent out, the associated costs (labor, materials) are categorized as internal failure costs. External failure costs occur after the customer receives the product.

A robust control plan must specify what is being controlled, how it is measured (method and frequency), and what to do if it goes out of control (the reaction plan). The original project champion and the budget from a previous phase are historical data and not active components of the ongoing control plan.