I can't begin to tell you how helpful the articles in your knowledge base have been to me and my company. I've taken a lot of statistics, in college, grad school, Lean Six Sigma Black Belt certification courses, corporate training, etc, and the explanations you have provided are by far the best SPC resources I've encountered. I particularly appreciate your use of actual examples with numbers that I can copy down in an Excel spreadsheet and review to enhance my own understanding of the material. You have provided an excellent service to the SPC community!"

Newton B. Green II, PE, PMP, DEE
Advisory Engineer – Quality Director
NovaTech USA

knowledge ladyBelow are our past publications (dating back to January 2004) as well as articles. The publications contain the featured topic for the month. The articles are pdf files.  If you would like to search our publications by category instead of by month, please select this link.  Select the "Subscribe" button to the right to sign-up for our monthly publications.

Learn More About SPC for Excel


How to Monitor Measurement Systems Over Time (May 2023)

Control Charts and Tornadoes (April 2023)

Variation and Histograms (March 2023)

The Impact of Out of Control Points on Baseline Control Limits (February 2023)

SPC and Global Warming: 1880 – 2022 (January 2023)


Item Analysis (December 2022)

Which Out of Control Tests Should I Use? (November 2022)

The Impact of Bar Width on Histograms (October 2022)

Understanding Regression Statistics – Part 2 (September 2022)

Understanding Regression Statistics – Part 1 (August 2022)

What Do I Work on First: Process or Measurement? (June 2022)

Analysis of Variance (ANOVA) and the Variability Chart (May 2022)

Process Capability and Variation (April 2022)

Ten Things to Know When Using the Individuals Control Charts (March 2022)

Control Limits and Specifications: The Four Process States (February 2022)

SPC and Global Warming: 1880 – 2021 (January 2022)


Individuals Control Charts and Levey- Jennings Charts (December 2021)

Modified Levene's Test for Equality of Variances (November 2021)

The g Chart vs the Individuals Chart (October 2021)

Is Overall Equipment Effectiveness (OEE) an Effective Metric? (September 2021)

2021Comparing X-mR and Xbar-R Control Charts (August 2021)

The Average Run Length and Detecting Process Shifts (July 2021)

Dashboards, KPIs and Noise (June 2021)

Control Charts and Adjusting a Process (May 2021)

Comparing XBar-R and XBar-s Control Charts (April 2021)

Plotting the Data and Immigration (March 2021)

The Calculations Behind a Gage Linearity Study (February 2021)

SPC and Global Warming: 1880 to 2020 (January 2021)


What Do the Process Capability/Performance Metrics Measure? (December 2020)

How Does Measurement Variation Impact Control Chart Signals? (November 2020)

Medians and the Individuals Control Chart (October 2020)

Laney u' Control Chart (September 2020)

2020Poisson Process Capability (August 2020)

Binomial Process Capability (July 2020)

Global Warming: A Trend or Step Changes? (June 2020)

COVID-19 Data: Does a Control Chart Add Anything to the Analysis? (May 2020)

COVID-19 Data and Variation (April 2020)

A Tale of Two Precision to Tolerance Ratios (March 2020)

The Problem of In Control But Out of Specifications (February 2020)

Variable and Two-Level Pareto Diagrams (January 2020)


Operator-Part Interaction in Gage R&R Studies (December 2019)

Five Common Mistakes with Gage R&R Studies (November 2019)

Multivariate Control Charts: The Hotelling T2 Control Chart (October 2019)

The Analysis of Mean Moving Ranges - ANOMmR (September 2019)

2019How to Mess Up Control Charts (August 2019)

Evaluating the Measurement Process (EMP) Overview (July 2019)

The Short EMP Study (June 2019)

Laney p' Chart (May  2019)

Analysis of Individual Values - ANOX (April 2019)

Nonparametric Techniques for Comparing Processes (March 2019)

Nonparametric Techniques for a Single Sample (February 2019)

The Analysis of Means and Ranges (January 2019)


Remembering Dr. W. Edwards Deming (December 2018)

The Difficulty of Setting Baseline Data for Control Charts (November 2018)

Fractional Factorial Designs - Part 2 (October 2018)

Fractional Factorial Designs - Part 1 (September 2018)

2018Baseball Has Changed – The Demise of the Complete Game and Other Tidbits (August 2018)

Scatter Diagrams (July 2018)

Pareto Charts (June 2018)

Operational Definition of a Consistent Measurement System (May 2018)

Acceptance Criteria for Measurement System Analysis (April 2018)

SPC and Global Warming - 2017 Update (March 2018)

Control Charts and Goals (February 2018)

The Impact of Measurement Error on Control Charts (January 2018)


Control Charts, ANOVA and Variation (December 2017)

SPC and the Lab (November 2017)

Process Flow Diagrams (October 2017)

Time and Muda (September 2017)

2017Dr. Ishikawa’s Seven Quality Tools (August 2017)

Three Sigma Limits and Control Charts (July 2017)

Descriptive Statistics (June 2017)

Control Charts and the Central Limit Theorem (May 2017)

Attribute Control Charts in Health Care (April 2017)

Interpretation of Alpha and p-Value (March 2017)

SPC and Global Warming Update (February 2017)

Applying the Out of Control Tests (January 2017)


A Look Back at Variation (December 2016)

Just Because There is a Correlation, Doesn't Mean .. (November 2016)

Deciding Which Distribution Fits Your Data Best (October 2016)

Distribution Fitting (September 2016)

2016How Much Data Do I Need to Calculate Control Limits (August 2016)

Box-Cox Transformation (July 2016)

What?  My Data are Not Normal? (June 2016)

Specifications and Measurement Error (May 2016)

Probable Error and Your Measurement System (April 2016)

Control Chart Rules and Interpretation (March 2016)

Are Skewness and Kurtosis Useful Statistics (Revisited - February 2016)

Trend Control Charts and Global Warming (January 2016)


SPC and Global Warming (December 2015)

Monitoring Destructive Test Method (November 2015)

SPC and Selecting a Supplier (October 2015)

Stepwise Regression (September 2015)

2015Horse Racing and Listening to Control Charts (August 2015)

z-mR Control Charts for Short Production Runs (July 2015)

How Many Samples Do I Need? (June 2015)

Hypothesis Testing (May 2015)

Comparing Individuals Charts to Attribute Charts (April 2015)

My Blood Pressure is What??? (March 2015)

Three Methods to Analyze Gage R&R Studies (February 2015)

Evaluating the Measurement Process - Part 2 (January 2015)


Evaluating the Measurement Process - Part 1 (December 2014)

It is the Operator's Fault! (November 2014)

Problem Solving Tools and M&M's (October 2014)

Keeping the Process on Target: EWMA Charts (September 2014)

2014Keeping the Process on Target: CUSUM Charts (August 2014)

Process Capability and Non-Normal Data (July 2014)

Control Charts and Non-Normal Data (June 2014)

Cpk vs Ppk: Who Wins (May 2014)

Cpk Alone is Not Sufficient (April 2014)

An Interactive Look at Process Capability (March 2014)

The Theory of Constraints (February 2014)

Affinity Diagrams (January 2014)


Top Ten SPC Questions (December 2013)

Process Analysis (November 2013)

Destructive Gage R&R Analysis (October 2013)

Gage R&R for Non-Destructive and Destructive Test Methods (September 2013)

2013Control Charts and Website Data (August 2013)

SPC and Your Suppliers (July 2013)

When an Average Isn't the Average (June 2013)

Just Plot the Data - It is So Simple! (May 2013)

Making Sense of Data: SPC and Aviation (April 2013)

Kaizen and SPC (March 2013)

SPC and Rational Subgrouping (February 2013)

SPC, Rational Subgrouping, and Golf (January 2013)


SPC and Jeopardy (December 2012)

The Estimated Standard Deviation and Control Charts (November 2012)

ANOVA Gage R&R - Part 3 (October 2012)

ANOVA Gage R&R - Part 2 (September 2012)

2012ANOVA Gage R&R - Part 1 (August 2012)

SPC for Excel Newsletters - A Review (July 2012)

My Process is Out of Control!  Now What Do I Do? (June 2012)

Control Charts and Purchasing (May 2012)

Control Charts and Surveys (April 2012)

Variation, People and Pay for Performance (March 2012)

Cpk Improvement Methodology (February 2012)

Returning to the Basics: Variation (January 2012)


SPC, Downtime, and Overall Equipment Effectiveness (December 2011)

Control Charts and America's Favorite Pastime - Baseball (November 2011)

Balancing People and Process (October 2011)

But, You Can't Measure What I Do! (September 2011)

2011When to Calculate, Lock, and Recalculate Control Limits (August 2011)

KPIs, Control Charts and Linking of Measurements (July 2011)

Anderson-Darling Test for Normality (June 2011)

Scatter Plot Matrix (May 2011)

Correlation Analysis (April 2011)

The Purpose of Control Charts (March 2011)

g Control Chart (February 2011)

Xbar-mR-R (Between/Within) Control Chart (January 2011)


Teaching Variation to Leadership (December 2010)

Using Pareto Diagrams and Control Charts Together (November 2010)

Polls, Sample Size and Error Margin (October 2010)

Control Limits - Where Do They Come From? (September 2010)

2010Levey-Jennings Chart (August 2010)

Waterfall Charts (July 2010)

Attribute Gage R&R Studies: Part 2 (June 2010)

Attribute Gage R&R Studies: Comparing Appraisers (May 2010)

Design of Experiments in Pharmaceutical Development (April 2010)

Experimental Design Techniques - Part 3 (March 2010)

Experimental Design Techniques - Part 2 (February 2010)

Experimental Design Techniques - Part 1 (January 2010)


SPC Newsletters - A Review (December 2009)

Measurement Systems - Is Yours Any Good (November 2009)

SPC and Pharmaceutical Finished Product Quality Specifications  (October 2009)

SPC and Pharmaceutical In-Process Control (September 2009)

2009An Example of the Misuse of SPC in Health Care (August 2009)

Bartlett's Test for Equality of Variances (July 2009)

Normal Probability Plots (June 2009)

Normal Distribution (May 2009)

Attributes Control Charts (April 2009)

np Control Charts (March 2009)

The Red Beads: Understanding Variation (February 2009)

Comparing Multiple Process Means: Bonferroni's Method (January 2009)


Single Factor ANOVA (December 2008)

SPC and Customer Service (November 2008)

Xbar-s Control Charts - Part 2 (October 2008)

Xbar-s Control Charts - Part 1 (September 2008)

2008Review of Past Newsletters (August 2008)

Linear Regression - Part 2 (July 2008)

Linear Regression - Part 1 (June 2008)

Failure Mode and Effects Analysis (May 2008)

Are the Skewness and Kurtosis Useful Statistics? (April 2008)

Small Sample Case for c and u Control Charts (March 2008)

Small Sample Case for p and np Control Charts (February 2008)

Another Look at Variation (January 2008)


Variables Measurement Systems - Part 4: Gage R&R (December 2007)

Variables Measurement Systems - Part 3: Linearity (November 2007)

Variables Measurement Systems - Part 2: Bias (October 2007)

Variable Measurement Systems - Part 1: Stability (September 2007)

2007SPC & Process Improvement in the Warehouse (August 2007)

u Control Charts (July 2007)

SPC and On-Time Performance (June 2007)

Rare Events and X-mR Charts (May 2007)

Chunky Data and Control Charts (April 2007)

Box and Whisker Plots (March 2007)

Comparing Multiple Processes (February 2007)

Dr. Deming and Profound Knowledge - Part 4 (January 2007)


Dr. Deming and Profound Knowledge - Part 3 (December 2006)

Dr. Deming and Profound Knowledge - Part 2 (November 2006)

Process Management Model (November 2006)

Dr. Deming and Profound Knowledge - Part 1 (October 2006)

Individuals Control Charts (October 2006)

Paired Sample Comparison (September 2006)

2006Comparing Two Processes (August 2006)

Over-controlling a Process: The Funnel Experiment (July 2006)

Monitoring Customer Complaints Using SPC (June 2006)

Monitoring Test Methods Using SPC (May 2006)

Selecting the Right Control Chart (April 2006)

Revisiting Variation (March 2006)

The Impact of Statistical Control (February 2006)

Histograms - Part 2 (January 2006)


Histograms - Part 1 (December 2005)

Analyzing Cause and Effect Diagrams (November 2005)

Creating Cause and Effect Diagrams (October 2005)

Inspecting Supplier Material (September 2005)

2005Explaining Standard Deviation (August 2005)

p Control Charts (July 2005)

Rational Subgrouping and Xbar-R Charts - Part 2 (June 2005)

Rational Subgrouping and Xbar-R Charts (May 2005)

Xbar-R Charts - Part 2 (April 2005)

Xbar-R Charts - Part 1 (March 2005)

Scatter Diagrams (February 2005)

Use of Control Charts (January 2005)


Process Capability - Part 3 (December 2004)

Process Capability - Part 2 (November 2004)

Process Capability - Part 1 (October 2004)

Data Collection (September 2004)

2004Control Strategies (August 2004)

c Control Charts (July 2004)

Pareto Diagrams (June 2004)

Problem Solving Model (May 2004)

Interpreting Control Charts (April 2004)

Operational Definitions/Measurement System Analysis (March 2004)

Leadership and Variation (February 2004)

Variation (January 2004)


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Articles Presented at National Conferences

"Using Time Series Charts to Analyze Financial Data" - this paper was presented at the Annual Quality Congress and describes how one company has used time series charts to analyze financial data (from the monthly profit and loss statement). (Download size: 375 KB)

"Cutting Costs, Not Employees" - this paper describes how organizations can cut costs without cutting employees; it also describes the role of the quality professional in making this happen. (Download size: 400 KB)

"Process Management" - this paper was presented at the Annual Quality Congress and shows how one company is using Process Management as its method to embed quality into the culture of the company, to run its business, to optimize systems and to reach its vision. At the heart of Process Management is a five-step method that is applied to each primary process: define, document, measure, manage and improve. The model represents a blend of process and people skills, which include statistical analysis of processes, teamwork, and team styles. (Download size 275 KB)

"Quality Skills Training: A Roadmap For Learning" - this paper was presented at the Annual Quality Congress. The purpose of this paper is to provide a blueprint for conducting monthly quality training to all associates. The major component of this blueprint is called Quality Skills Training (QST). QSTs are one and half-hour training sessions. This paper describes how these training sessions are designed and includes a teaching guide for one topic: creativity. This paper is designed to be part of an interactive session where the QST on creativity is presented as part of the blueprint. (Download size 378 KB)

"Develop Effective Metrics for Supply Management" - this paper was presented at the 90th Annual International Supply Management Conference. Metrics are used to know where you are, where you have been and where you are going. This paper examines a process for selecting metrics based on the organization's vision. The best way to know if a metric is changing is to examine the data over time using time-series charts. A ten-step process to implement metrics is also presented. (Download size 61KB)


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