Issue: Volume 7, Number 10
Date: October 2007
From: Mark J. Anderson, Stat-Ease, Inc., Statistics Made Easy® Blog

Dear Experimenter,

Here's another set of frequently asked questions (FAQs) about doing design of experiments (DOE), plus alerts to timely information and free software updates. If you missed the previous DOE FAQ Alert, please click on the links at the bottom of this page. If you have a question that needs answering, click the Search tab and enter the key words. This finds not only answers from previous Alerts, but also other documents posted to the Stat-Ease web site.

Feel free to forward this newsletter to your colleagues. They can subscribe by going to If this newsletter prompts you to ask your own questions about DOE, please address them via mail

For an assortment of appetizers to get this Alert off to a good start, see these new blogs at
—Statistics so simple that only a child can do it
—Fantasy football—addicting to a sports fan who loves stats
—Assessing the risk versus benefit of wearing seat belts
—Jokes about scientists and statisticians who are powerfully driven to repeat bad things

Topics in the body text of this DOE FAQ Alert are headlined below (the "Expert" ones, if any, delve into statistical details).

1. Newsletter Alert: September issue of the Stat-Teaser offers an intoxicating article on how to mix a tasty beer cocktail
2. FAQ: Why no red line on diagnostic plot for leverage?
3. Webinar Alert: Sizing RSM and Mixture Designs for Adequate Precision via use of Fraction of Design Space (FDS) Plots
4. Free Books (US/Canada Only): Enter drawing for 2 copies of Box & Drapers' "Empirical Model-Building and Response Surfaces" and 2 signed "RSM Simplified" primers by Anderson & Whitcomb
5. Info Alert: "Adhesives & Sealants Industry" DOE case study
6. Events Alert: Several talks and exhibits the next 4 weeks!
7. Workshop Alert: See when and where to learn about DOE

PS. Quote for the month: Scientists crave unpredictability according to theoretical physicist Freeman Dyson. (Page through to the end of this e-mail to enjoy the actual quote.)


1. Newsletter Alert: September issue of the Stat-Teaser offers an intoxicating article on how to mix a tasty beer cocktail

Many of you will soon receive a printed copy of the latest Stat-Teaser, but others, by choice or because you reside outside of North America, will get your only view of the September issue at It features an article by me titled "Mixture Design Brews Up New Beer Cocktail—Black & Blue Moon," which details how I made use of mixture design for the optimal formulation* of three distinct beers.

This issue of the Stat-Teaser also provides a primer on power titled "No More Under-Sized Factorials via Shari's Favorite New Tool." It shows how to make use of new features in version 7.1 of Stat-Ease software. Check this out via the newly-revised online tour of the Design-Expert® program posted at along with a free trial of the software itself—fully-functional for 45 days of use. The last page of the newsletter features the new second edition of "DOE Simplified." See for details on this fun, but very informative primer on DOE. Link from there to purchase it on line.

PS. The October 3, 2007, issue of ASQ Weekly features "DOE Simplified" as their Book of the Week. :)

*(Learn more about mixture design by attending the three-day computer-intensive workshop "Mixture Design for Optimal Formulations." For a complete description of this class, see Link from this page to the course outline and schedule. Then, if you like, enroll online.)


2. FAQ: Why no red line on diagnostic plot for leverage?

-----Original Message-----
From: US Air Force
"Thanks for your previous support—I learned a lot. Now I am working up a model with fewer runs—a number of these proved to be outliers. However, when reviewing the diagnostics, although everything else looks good, the leverage plot comes back with no red line, even though all points fall below 1. How do I interpret a chart like this?"

Answer (from Stat-Ease Consultant Pat Whitcomb):

"Our DOE software draws the red line at two times the average leverage. However, the maximum leverage a point can have is one. Therefore, no red line can be drawn when the average leverage is equal to or greater than one half. The average leverage is equal to the number of coefficients (including the intercept) in your model divided by the number of runs in your design. When you delete or ignore runs, all the leverages go up, but those closest to the area of the removed runs go up much more than those farther away. Also, if you do model reduction, the high leverage points for the coefficients that are removed then become low leverage points. For these reasons, you generally see more spread in leverages when analyzing a completed experiment (assuming you have missing runs and/or reduce the model) then you do when evaluating the initial (planned) design."

PS. For more detail on leverage, see this year's May DOE FAQ Alert, FAQ #1 at and follow the links provided afterward.

(Learn more about leverage by attending the three-day computer-intensive workshop "Experiment Design Made Easy." See for a description of this class and then link from this page to the course outline and schedule. Then, if you like, enroll online.)


3. Upcoming Webinar: Sizing RSM and Mixture Designs for Adequate Precision via use of Fraction of Design Space (FDS) Plots

You are invited to attend a free web conference by Stat-Ease on "Sizing RSM and Mixture Designs for Adequate Precision via use of Fraction of Design Space (FDS) Plots" at 8 AM Central USA Time on
Wednesday, November 28 and again at 11 AM Thursday, November 29. It will be based on a talk Pat presented this September in Dortmund, Germany to ENBIS (European Network of Business and Industry Statistics).

Unique to this 'webinar' will be demonstrations of upgraded FDS features in our latest revision of
Design-Expert software—V7.1. Attendance may be limited for one or both of these two one-hour
webinar sessions. Contact our Communications Specialist Karen Dulski via to sign up. If you can be accommodated, she will send you the link for the WebConnect and dial-in for ConferenceNow voice via telephone. Toll-free access extends world wide, but not to all countries. Details will be provided as needed. Here's an example of a real-life problem that might benefit by seeing the FDS plot, especially a permutation Pat developed that calculates fraction of paired design space ("FPDS").

-----Original Message-----
From: Six Sigma Black Belt
"I'm out of the office and a product developer is in a hurry so he can't wait until I come back to review his mixture design. He initially sets up a design in the space he thinks makes the most sense. The design evaluation guidelines with regard to standard error, VIF and power freak him out, so he opens up the range on the third component to give a more balanced design and improves those design evaluation criteria. This wider-ranging experiment is actually run and the data confirms that he was right initially—the new expanded design space does not generate product we can test. :( We need to run a new experiment to really try and optimize within our original space. Because the components will not vary over the same range, I know there will be some colinearity. Is there any way to get good power and VIF values within the design space that makes sense? Also, I assume that D-optimal is my preferred choice of designs as well.

Pat addressed this concern in his MINI PAPER (abridged by me) on "Interpreting Power in Mixture DOE—Simplified"—see . Now, via this webinar, Pat provides a possible remedy.


4. Free books (US/Canada only): Enter drawing for 2 copies of Box & Drapers' "Empirical Model-Building and Response Surfaces" and 2 signed "RSM Simplified" primers by Anderson & Whitcomb

(Sorry, due to the high cost of shipping, this offer applies only to residents of the United States and Canada.)

Simply reply to this e-mail by October 26 if you'd like a free copy of Box and Drapers' classic statistical text "Empirical Model-Building and Response Surfaces." Originally published in 1987 (John Wiley and Sons, New York), this book is a classic in the field of response surface methods (RSM) for process optimization. However, for workshops on this topic,* Stat-Ease now uses Myers and Montgomerys' "Response Surface Methods." Furthermore, in the recently-published "Response Surfaces, Mixtures and Ridge Analysis," George E. P. Box, Norman R. Draper offer much more than their previous RSM textbook—857 pages worth!

A drawing will also be held for two autographed copies of "RSM Simplified: Optimizing Processes Using Response Surface Methods for Design of Experiments." These two books will be signed by the authors (myself and Stat-Ease consultant Patrick Whitcomb). For more information on this soft cover 'how-to' primer, see

In your e-mail, feel free to specify which of these two titles you would like. (Reminder: If you reside outside the US or Canada, you are NOT eligible for the drawing because it costs too much to ship the books.) For a complete list of books offered for sale by Stat-Ease, go to its e-commerce site at

*(Learn more about RSM by attending the three-day computer-intensive workshop "Response Surface Methods for Process Optimization." See for a complete description. Link from this page to the course outline and schedule. Then, if you like, enroll online.)


5. Info Alert: "Adhesives & Sealants Industry" DOE case study

The latest issue of "Adhesives & Sealants Industry" features a case study on a designed experiment that significantly reduced downtime in a masking-tape production process. It investigated five potential causes in a fractional two-level factorial. The results demonstrated that the line would run without problems by simply compensating for temperature changes. See this story at, along with many other helpful case-studies, as well as 'how-to' and statistical publications on design of experiments.


6. Event alert: Several talks and exhibits the next 4 weeks!

At the 51st Fall Technical Conference (FTC) in Jacksonville, Florida on October 11-12 Pat Whitcomb will talk about "Graphical Selection of Effects in General Factorials." I will make an appearance as the presenter of Jeff Hybarger's presentation on "The Ten Most Common Designed Experiment Mistakes." (He couldn't make it.) Pat and I will also man a tabletop display for Stat-Ease. See for all the details on FTC.

I am presenting a talk on "DOE for Ruggedness Testing" at the Minnesota Quality Conference in Bloomington on October 15. I will also help our Marketing Director, Heidi Hansel, staff the Stat-Ease exhibit.

The next day, October 16, Stat-Ease Consultant Shari Kraber presents a one-day workshop on "DOE for Design for Six Sigma (DFSS)" with assistance by her colleague Wayne Adams. See for conference details.

The MD&M (Medical Design & Manufacturing) conference in Minneapolis on October 17-18 will feature a display by Stat-Ease at Booth 1149. For a complimentary pass to the 'expo' hall, go to

At the ISMI Symposium on Manufacturing Effectiveness in Austin, Texas on October 24, I will give a presentation on "Dual Response Surface Methods (RSM) to Make Processes More Robust." I will also put up a tabletop display to show attendees of the Sematech conference what Stat-Ease can offer to make their semiconductor-related experimentation more effective. For more details on this symposium, see

Stat-Ease consultant John Guerin will represent us at the 13th Annual International Validation Week in Philadelphia on October 23-25. Follow this link to details on the conference.

Wayne Adams hits the road to offer a poster session on "Methods for Sizing Designed Experiments" at the Design and Analysis of Experiments (DAE) conference in Memphis from October 31 through November 3. He will also demonstrate Stat-Ease DOE software and provide an exhibit. The home page for DAE can be found at

Click for a list of appearances by Stat-Ease professionals. We hope to see you sometime in the near future!


7. Workshop alert: See when and where to learn about DOE

Here is the Fall lineup of our DOE classes:

—Experiment Design Made Easy (EDME) (Detailed at
October 9-11 (Minneapolis, MN)—Seats still open!
December 4-6 (Minneapolis)—Enjoy our winter wonderland!*

*(If you prefer somewhere warmer, enroll in the San Diego EDME onJanuary 22-24.)
—Mixture Design for Optimal Formulations (MIX) (
October 23-25 (Minneapolis)—Hits the sweet spot!

—Response Surface Methods for Process Optimization (RSM) (
November 13-15 (Minneapolis)—By popular demand!

—DOE for DFSS: Variation by Design
November 7-8 (Minneapolis)—Six Sigma Black Belts love it!

See for complete schedule and site information on all Stat-Ease workshops open to the public. To enroll, click the "register online" link on our web site or call Elicia at 612.746.2038. If spots remain available, bring along several colleagues and take advantage of quantity discounts in tuition. Or, consider bringing in an expert from Stat-Ease to teach a private class at your site.*

*Once you achieve a critical mass of about 6 students, it becomes very economical to sponsor a private workshop, which is most convenient and effective for your staff. For a quote, e-mail


I hope you learned something from this issue. Address your general questions and comments to me at:



Mark J. Anderson, PE, CQE
Principal, Stat-Ease, Inc. (
2021 East Hennepin Avenue, Suite 480
Minneapolis, Minnesota 55413 USA

PS. Quotes for the month—Scientists crave unpredictability according to theoretical physicist Freeman Dyson:

"Science is organized unpredictability. The best scientists like to arrange things in an experiment to be as unpredictable as possible, and then they do the experiment to see what will happen."
— Freeman Dyson

Trademarks: Design-Ease, Design-Expert and Stat-Ease are registered trademarks of Stat-Ease, Inc.

Acknowledgements to contributors:
—Students of Stat-Ease training and users of Stat-Ease software
—Stat-Ease consultants Pat Whitcomb, Shari Kraber and Wayne Adams (see for resumes)
—Statistical advisor to Stat-Ease: Dr. Gary Oehlert (
—Stat-Ease programmers, especially Tryg Helseth and Neal Vaughn (
—Heidi Hansel, Stat-Ease marketing director, and all the remaining staff


Interested in previous FAQ DOE Alert e-mail newsletters?
To view a past issue, choose it below.

#1 Mar 01, #2 Apr 01, #3 May 01, #4 Jun 01, #5 Jul 01 , #6 Aug 01, #7 Sep 01, #8 Oct 01, #9 Nov 01, #10 Dec 01, #2-1 Jan 02, #2-2 Feb 02, #2-3 Mar 02, #2-4 Apr 02, #2-5 May 02, #2-6 Jun 02, #2-7 Jul 02, #2-8 Aug 02, #2-9 Sep 02, #2-10 Oct 02, #2-11 Nov 02, #2-12 Dec 02, #3-1 Jan 03, #3-2 Feb 03, #3-3 Mar 03, #3-4 Apr 03, #3-5 May 03, #3-6 Jun 03, #3-7 Jul 03, #3-8 Aug 03, #3-9 Sep 03 #3-10 Oct 03, #3-11 Nov 03, #3-12 Dec 03, #4-1 Jan 04, #4-2 Feb 04, #4-3 Mar 04, #4-4 Apr 04, #4-5 May 04, #4-6 Jun 04, #4-7 Jul 04, #4-8 Aug 04, #4-9 Sep 04, #4-10 Oct 04, #4-11 Nov 04, #4-12 Dec 04, #5-1 Jan 05, #5-2 Feb 05, #5-3 Mar 05, #5-4 Apr 05, #5-5 May 05, #5-6 Jun 05, #5-7 Jul 05, #5-8 Aug 05, #5-9 Sep 05, #5-10 Oct 05, #5-11 Nov 05, #5-12 Dec 05, #6-01 Jan 06, #6-02 Feb 06, #6-03 Mar 06, #6-4 Apr 06, #6-5 May 06, #6-6 Jun 06, #6-7 Jul 06, #6-8 Aug 06, #6-9 Sep 06, #6-10 Oct 06, #6-11 Nov 06, #6-12 Dec 06, #7-1 Jan 07, #7-2 Feb 07, #7-3 Mar 07, #7-4 Apr 07, #7-5 May 07, #7-6 Jun 07, #7-7 Jul 07, #7-8 Aug 07, #7-9 Sep 07, #7-10 Oct 07 (see above)

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