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Dictionary of Lean Six Sigma Tools/Concepts

There are 23 entries in this dictionary.
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Term Definition
Sample Data

A subset of the population that is generally a fair representation of that population. A Sample Size Calculator can be used to help estimate how much data is needed to fairly represent the population. An adequate sample can allow someone to make reasonable inferences about the population. 
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #6 - Population vs. Sample Data

Sample Size Calculator

A statistical tool that returns the number of samples required in order to achieve a certain level of confidence and precision (a.k.a. margin of error) for a population with a given portion of defects or standard deviation. It can be calculated on both continuous or discrete values. The version provided by StatStuff is unique because it can return either the level of confidence or precision for you if you already have a given sample size.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #19 - Calculating a Sample Size

Scope

The boundaries of the project by defining what the project should focus on (includes) and shouldn't focus on (excludes). The purpose is to remind and unify the team around what specific problem they're trying to fix, to keep the project at a manageable level (not too big or too small), and to prevent the project from driving in the wrong direction (i.e., avoiding "scope creep").
Related StatStuff Video: 
   -Section 4-Define Phase, Lesson #3 - Defining a Project Scope

Scorecards

A report that measures the critical metric(s) for piloted or implemented improvements. It usually includes only one or two metrics (e.g., they output Y for the process being improved), often includes the targets for what's being measured, and generally tracks the metric over time (trending) to monitor progress.
Related StatStuff Video: 
   -Section 8-Control Phase, Lesson #2 - Building a Scorecard

Short Term Data

Data that generally covers a shorter snapshot of time, is collected from within a sub-group, and often includes only common causes (i.e., little or no special cause variation). Compare with long term data.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #17 - Variation Over Time (Short/Long Term Data)

Sigma Level

Also known as the Z score, it measures the voice of the process (VOP) in relation to the voice of the customer (VOC). In a sense, it measures the "severity of pain" in the process not meeting the customer's requirements. Technically, it measures the number of standard deviations a data point (like the upper specification limit or USL) is from the mean. The calculation is ((X - μ) / σ) where X is an observation like the USL.
Related StatStuff Video: 
   -Section 6-Analyze Phase, Lesson #5 - Process Capability: Step 4 (Normal Distributions)

SIPOC

It's an extension of the IPO Flow Model by identifying the Supplier (S) providing the inputs and the Customer (C) receiving the outputs. The purpose is to identify the required inputs and all possible sources providing those inputs, to identify the high-level critical steps in the business process, and to identify the ultimate customer or receiver of the outputs created by the process. Altogether it helps visualize the relationship of the entire process from the Supplier to the Customer. Some people prefer to reverse it instead and follow a COPIS as a way of starting with the customer and working backwards.
Related StatStuff Video: 
   -Section 4-Define Phase, Lesson #5 - Building a SIPOC

Six Sigma

It either refers to a method or a measurement.  

As a method, it helps improve business operations by focusing on the effectiveness (quality or accuracy) of the output from a business process. It does this by finding ways to reduce variation in order to help reduce defects (instances that fall outside customer's requirements). The most common approach to applying it is the DMAIC methodology.

As a measurement, it is a statistical reference to having six standard deviations (sigmas) between the process mean and the customer requirements (i.e., LSL/USL). Having more sigmas in the process means there is very little variation and is generally referred to as having only 3.4 defects per million opportunities (DPMO) or being 99.9997% accurate. 
Related StatStuff Videos: 
   -Section 1-Introduction, Lesson #2 - Introduction to Lean and Six Sigma
   -Section 3-Overview, Lesson #3 - Overview of Statistical Terms and Concepts

Sixpack Process Capability

Also known as the "Process Capability Sixpack", it's a unique statistical tool from Minitab that combines the tests for stability, normality, and process capability in one simple chart. 
Related StatStuff Video: 
   -Section 6-Analyze Phase, Lesson #5 - Process Capability: Step 4 (Normal Distributions)

SOPs (Standard Operating Procedures)

A detailed documentation outlining the process steps in accordance with business policies and regulations. For a LSS project, these should be created (normally near the end of project) after a new process has been improved and implemented to ensure those improvements are sustained. 
Related StatStuff Video: 
   -Section 8-Control Phase, Lesson #10 - Documenting a New Process with SOPs

Spaghetti Diagram

A visual mapping of the Transportation (path of a product's movement) or Motion (path of equipment or operator movement), two of Lean's 7 Deadly Wastes, in a process in order to expose potential waste. It usually is a floorplan of the area involved in the movement with a drawing of the actual transportation or motion occurring over time.
Related StatStuff Video: 
   -Section 2-Lean, Lesson #9 - Spaghetti Diagram

SPC (Statistical Process Control)

A method of measuring process data over time in order to find and fix special causes. Control charts are often used to help detect these special causes (using special cause variation testing).
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #15 - Statistical Process Control (SPC)

Special Cause Variation

A type of variation (a.k.a. Signal or Anomaly) that reflects unnatural or erratic variability that generally comes from outside the process.  Some examples include variation caused by a power surge, extreme weather conditions, system/computer malfunctions, poor batch of raw materials, etc. This can be contrasted with Common Cause Variation.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #14 - Variation Causes (Common vs. Special)

Special Cause Variation Testing

A method of applying a set of tests to a process to see if special causes exist. The method includes eight common tests typically applied to a control that splits the area into 3 zones (called A, B, & C) representing one standard deviation away from the mean. The tests evaluate the variation of the process and look for the following occurrences in the data: 1) any data point outside the control limits, 2) nine data points in a row on the same side of the mean, 3) six data points in a row either all increasing or decreasing, 4) fourteen data points in a row alternating up and down, 5) two of three consecutive data points on the same side of the mean in zone A or beyond, 6) four of five consecutive data points on the same side of the mean in Zone B or beyond, 7) fifteen consecutive data points within Zone C on either side of the mean, and 8) eight consecutive data points outside of Zone C on either side of the mean.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #16 - Testing for Special Cause Variation

Sponsor

The highest external resource level in a project, it's usually the role given to an executive such as a Director, Vice President, or higher. They ultimately own the process targeted by the project and often serve as the final decision maker for getting resources and removing roadblocks. Communication with them by the LSS project leader tends to be infrequent (i.e., perhaps 2 to 5 times during the project).
Related StatStuff Video: 
   -Section 1-Introduction, Lesson #8 - Key Roles in a Lean or Six Sigma Project

Spread

A statistical reference for the measurement of distance each data point is from the central tendency (e.g., mean, median or mode). Typical measurements include range, deviation, variance, and standard deviation.
Related StatStuff Videos: 
   -Section 5-Measure Phase, Lesson #12 - Spread
   -Section 5-Measure Phase, Lesson #8 - Distributions: Overview

Stability Factor

The relative spread of data point about the median or (Q1 / Q3). It is commonly used when the data is non-normally distributed. The closer the factor is to 1, then the less like there is variation in the distribution
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #12 - Spread

Stakeholder Analysis (ARMI Tool)

A tool to help evaluate who the project stakeholders are and their level of support. ARMI is an acronym referencing the 4 different levels assigned to each stakeholder in the analysis which include 1) Approver of team decisions, 2) Resource whose expertise, skills, or clout may be needed, 3) Member of team with authority of the charter, and 4) Interested party who should be informed on direction and findings.
Related StatStuff Video: 
   -Section 4-Define Phase, Lesson #4 - Building a Project Team

Standard Deviation

The average distance to the mean for all data points. It is the most common measure of variation across entire datasets that are normally distributed. Statistically it represents the square root of the variance.
Related StatStuff Video: 
   -Section 5-Measure Phase, Lesson #12 - Spread

Statistical Test Drilldown

A chart that helps identify what statistical tool may be ideal based on the type and normality of the data being analyzed.
Related StatStuff Video: 
   -Section 6-Analyze Phase, Lesson #12 - Hypothesis Testing: Finding the Right Statistical Test

Stepwise Regression

A statistical test that analyzes multiple continuous (a.k.a. variable or numerical) values through several iterations to find what single or combination of factors yield the highest potential correlation on a primary output value.
Related StatStuff Video: 
   -Section 7-Improve Phase, Lesson #3 - Testing for Multicollinearity

Storyboard for a Project

A document (often comprised of a set of PowerPoint slides) that tells the "story" of the project. It generally summarizes the premise, analysis, and results of the project. It can be used during the project (for getting team/stakeholder buy-in) or as a post-project reference. There is no formal standard for documenting projects, although many companies with formal LSS programs may have their own internal standards.
Related StatStuff Video: 
   -Section 1-Introduction, Lesson #10 - Project Storyboard

Subject Matter Expert (SME)

An external resource in a project that usually isn't in any management role. They have direct and unique knowledge or experience for the process (or parts of the process) targeted by the project. Communication with them by the LSS project leader tends to vary depending on the need for their specialty.
Related StatStuff Video: 
   -Section 1-Introduction, Lesson #8 - Key Roles in a Lean or Six Sigma Project

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