Issue: Volume 7, Number 4
Date: April 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
— "You will never be happy if you continue to search for what happiness consists of."
— Statistics reinforce my happy choice for vacation destination
— El Morro’s twisty ternary bastions
— Pairing foods and beverages to please the palate

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: March issue of the Stat-Teaser features new release of Design-Expert® software
2. FAQ: Can responses with missing data still be analyzed?
3. Info Alert: "Space Shuttle Debris Impact Tool Assessment Using the Modern Design of Experiments"
4. Book Alert: Ryan's "Modern Experimental Design" and a new text by Box and Draper on response surface methods (RSM)
5. Event Alert: Stat-Ease out and about
6. Workshop Alert: See when and where to learn about DOE

PS. Quote for the month: Profound insights on RSM model-building offered by Box and Draper. (Page through to the end of this e-mail to enjoy the actual quote.)


1. Newsletter Alert: March issue of the Stat-Teaser features new release of Design-Expert software

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 March issue at

This issue of the Stat-Teaser features version 7.1 of Design-Expert (DX7.1). DX7.1 beefs up power and design capabilities and offers clever new interface features that make design and analysis easier than ever. For a free, fully-functional trial, click and/or view tutorials at See pricing for new licenses or upgrades at our e-commerce site:

Also featured in this issues of Stat-Teaser is the new DOE for DFSS: Variation by Design Workshop, which will achieve its inaugural presentation on June 20-21 at our Minneapolis training center. For more details on this class, see From there you can enroll on-line via internet e-commerce.


2. FAQ: Can responses with missing data still be analyzed?

-----Original Question-----
From: Sweden
"I am doing a normal 2^3 experiment with 2 replicates. I will not be able to use one of the response values. Can I make analysis in a normal way. I believe that your software gives you some kind of a warning!?"

"In situations like this, our Design-Expert and Design-Ease® software warns "Some columns have missing data. Rows with missing data will be ignored. Responses Ri." (Note: Newer versions of Stat-Ease software provide tools to ignore individual results in any particular response you tried to measure.) To continue, simply press "Yes." Then in V7 and newer versions the software will detect the loss of orthogonality caused in this case by the missing response and suggest you OK it to recalculate effects to see how the model coefficients change depend on the terms you choose after inspecting the half-normal and/or Pareto plots. Then via least squares regression it fits the model.* Feel free to email your data file with the missing response if you would like a second opinion on analysis. This is a free service provided by Stat-Ease to lend a hand to novice users or advanced ones that may be struggling with an especially difficult data set. It's best you because this goes to all of the Stat-Ease staff of DOE experts.

*In 1990, George Box wrote on "A Simple Way to Deal with Missing Observations from Designed Experiments" in Quality Engineering magazine (Vol. 3, #2, pp 249-254). Recognizing that not everyone had access to computers that provided regression tools — Box's first choice, he advised a simpler procedure to plug in a "fitted value" for the missing observation developed originally by Yates in 1933! We've come a long way over the four-score years since this pioneering work in the field of DOE.


3. Info Alert: "Space Shuttle Debris Impact Tool Assessment Using the Modern Design of Experiments"

Dick DeLoach of NASA Langley Research Center is lead author of an article detailing application of DOE tools to quantify the impact of cavity geometry error on estimates of thermal and structural reentry loads on the Space Shuttle. See this at The paper stemmed from a presentation to the 45th AIAA Aerospace Sciences Meeting earlier this year. The article credits Stat-Ease Consultants Wayne Adams and Pat Whitcomb for their "invaluable assistance in accounting for nonlinear factor constraints in the design of these experiments." :)

In the January 2006 issue of DOE FAQ Alert, Dick contributed a primer on "The Modern Design of Experiments in Three Laws." If you missed this at the time, I recommend you look it up at


4. Book Alert: Ryan's "Modern Experimental Design" and a new text by Box and Draper on response surface methods (RSM)

John Wiley & Sons just published two books on DOE and RSM

— "Modern Experimental Design" by Thomas P. Ryan: See details at Page 1 of the book states that "Software is almost indispensable in designing experiments...special purpose software...will be needed in some circumstances...with strong emphasis on Design-Expert, which has certain features reminiscent of expert systems..." :)

— "Response Surfaces, Mixtures and Ridge Analysis" by George E. P. Box, Norman R. Draper offers much more than their previous textbook "Empirical Model-Building and Response Surfaces" (1987), but at 857 pages it is very hefty! See more information at Note they included as problem 5-35 my DOE on a bread making machine that Quality Progress magazine published in their May 2003 issue.* I am proud to achieve mention in this book by Box and Draper. :)

*Manuscript at


5. Event Alert: Stat-Ease out and about

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

PS. Do you need a speaker on DOE for a learning session within your company or technical society at regional, national, or even international levels? If so, contact me. It may not cost you anything if Stat-Ease has a consultant close by, or if a web conference will be suitable. However, for presentations involving
travel, we appreciate reimbursements for airfare, hotel and meals — expenses only. In any case, it never hurts to ask Stat-Ease for a speaker on this topic. Contact if you have an event coming up with an open slot for a presentation.


6. Workshop Alert: See when and where to learn about DOE

See for 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 Stat-Ease at 1.612.378.9449. 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. Quote for the monthProfound insights on RSM model-building:

"The exact functional usually unknown and possibly unknowable...We have only to think of the flight of a bird, the fall of a leaf, or the flow of water through a valve, to realize that, even using such equations, we are likely to be able to approximate only the main features of such a relationship."
—Box and Draper, 1987, "Empirical Model-Building and Response Surfaces"
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 (see above)

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