Lean Six Sigma & Root Cause Analysis: Key Tools & Concepts

SWOT Analysis

A 4-quadrant technique that communicates the strengths, weaknesses, opportunities, and threats for a process.

DOWNTIME

An acronym for remembering the 8 wastes.

5 Whys

The most basic Root Cause Analysis tool.

5S

Five steps to transform a wasteful environment into a lean environment.

A3

A Japanese tool that summarizes an entire project on a single piece of paper.

Analyze

The 3rd step of a DMAIC project, where Root Cause Analysis is performed.

Attribute Data

One of the two types of data; known as 'count' data.

Bar Chart

A chart that best displays volume by category.

Benchmarking

Comparing best practices between categories.

Brainstorming

A group discussion designed to produce innovative ideas.

Buffer Time

Time between value-add process steps, often used to clean or prepare.

Causal Tree

A Root Cause Analysis tool that branches into multiple, undefined directions.

Change Management

An approach to prepare, support, and help individuals and organizations through change.

Charter

A document that summarizes the purpose of a project (Define phase).

Common Cause

Natural variation.

Continuous Improvement

Ongoing improvement of products, services, or processes.

Control

The 5th step of a DMAIC project, proving good changes can be sustained.

Control Plan

A document that outlines how to monitor and sustain improvements.

COPQ (Cost of Poor Quality)

Costs businesses experience from internal and external failures.

Correlation Analysis

Analysis that quantifies how strong a relationship is between two variables.

Cost of Quality

Costs incurred when investing in training, audits, and prevention activities.

Cost/Benefit Analysis

A 4-quadrant technique prioritizing activities based on cost and benefit.

CTQ (Critical to Quality)

Characteristics of products/services that customers find most valuable.

Cycle Time

The average time it takes to produce one unit.

Data

Facts or statistics gathered for analysis.

Data Collection Plan

A document that standardizes and plans data collection (Measure/Improve).

Defect

One of the 8 wastes: flaws in process outputs.

DMAIC

Define, Measure, Analyze, Improve, Control.

DMAD / DFSS

A project type used when a process can no longer be repaired.

DPMO

Quality measurement estimating failures per one million opportunities.

DPU

Quality measurement calculating average failures per unit produced.

External Failure

Process failures that reach the customer.

Extra Processing

One of the 8 wastes: more steps than needed.

FIFO (First In, First Out)

A process ensuring the oldest items are used first.

Histogram

A chart showing volume of variation by category.

Histogram with Normal Curve

A histogram displaying data spread along with a bell curve.

Hypothesis Testing

A test that uses data to challenge a theory.

Implementation Plan

A document managing corrective actions (Improve phase).

Improve

The 4th step of DMAIC where solutions are implemented.

Internal Failure

Failures caught inside the business before reaching customers.

Inventory

One of the 8 wastes: excess materials or finished goods.

Ishikawa Diagram (Fishbone)

A Root Cause Analysis tool shaped like a fish.

JDI (Just Do It)

Projects requiring no Lean/Six Sigma skill—simply implemented.

JIT (Just in Time)

Designing a process so materials arrive exactly when needed.

Kaizen

Japanese term for "good change"; a rapid improvement method.

Kanban

A visual card/signboard used to manage workflow.

KPI (Key Performance Indicator)

Measures performance toward a goal.

Lead Time

Time between when an order is placed and when it is received.

Lean

A methodology focused on waste reduction.

Lean Six Sigma

A problem-solving methodology combining waste and variation reduction.

Line Chart

A chart that best displays volume over time.

LSS Black Belt

Highly skilled in Lean and Six Sigma; leads major projects.

LSS Green Belt

Leads Lean projects within their scope; supports Black Belts.

LSS Master Black Belt

Expert who designs and leads Lean Six Sigma programs.

LSS Yellow Belt

An introductory certification; supports higher belt levels.

LTCA (Long-Term Corrective Action)

A corrective action that addresses root cause sustainably.

Measure

The 2nd step of DMAIC, where the problem is quantified.

Motion

One of the 8 wastes: unnecessary movement of people.

Muda

Japanese term for process waste.

NVA (Non-Value-Added Activity)

Activity that provides no customer value and should be eliminated.

NVAR (Non-Value-Added but Required)

Provides no value but is necessary; should be reduced.

Obeya

Japanese for "big room"; a space used to execute/showcase projects.

Operational Definitions

Standardized definitions used to ensure clarity.

Overproduction

One of the 8 wastes: producing more than demand.

Pareto Chart

A chart that displays volume by category, sorted high to low, with a cumulative line (80/20 rule).

Pilot

A corrective action test before full implementation.

PDCA (Plan, Do, Check, Act)

Four steps of a PDCA project.

Problem

When a process fails to meet expectations.

Process

Transforms inputs into outputs using resources.

Process Improvement

Identifying, analyzing, and improving processes.

Process Inputs

Materials, products, or services fed into a process.

Process Map

A tool that visualizes process steps in order.

Process Outputs

Products/services exiting a process.

RACI Matrix

A responsibility assignment matrix.

Regression Analysis

Quantifies relationships between two variables and produces an equation.

Sampling

Using a subset of data to represent a population.

Scatter Plot

A chart showing the relationship between two variables.

Sigma (σ)

Quantifies variation.

Sigma Levels

A quality score based on DPMO, with 6 being the best.

SIPOC

A high-level process map showing Suppliers, Inputs, Process, Outputs, Customers.

Six Sigma

A methodology focused on reducing variation.

Spaghetti Diagram

A tool showing movement of people/materials.

Special Cause

Variation caused by abnormal events.

Stakeholder

Anyone affected by or involved in a project.

STCA (Short-Term Corrective Action)

A temporary fix.

Storyboard

Tool for building presentations visually.

Suppliers

Provide process inputs.

Survey

A list of questions to gather data from people.

Takt Time

The rate at which a product must be produced to meet demand.

VA (Value-Added Activity)

Activity that adds value to the customer.

Value

Customer-defined importance or usefulness.

Value Stream

All activities required to deliver value to a customer.

Variable Data

Data measured on a scale.

Variation

Deviation from a standard.

VOC (Voice of the Customer)

Customer feedback on expectations and experiences.

VSM (Value Stream Map)

A tool visualizing the flow of materials/products.

Waiting

One of the 8 wastes: delays in process steps.

Waste

Any activity that consumes resources but adds no value.

Yokoten

Japanese term meaning to replicate a successful process elsewhere.