Issue: Volume 10, Number 4 (Circulation: Over 5500 worldwide)
Date: April 2010
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, see below.

==> Tip: Get immediate answers to questions about DOE via the Search feature on the main menu of the Stat-Ease® web site. This not only pores over previous alerts, but also the wealth of technical publications posted throughout the 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 to:

Also, Stat-Ease offers an interactive web site — the Support Forum for Experiment Design at Anyone (after gaining approval for registration) can post questions and answers to the Forum, which is open for all to see (with moderation). Furthermore, the Forum provides program help for Design-Ease® and Design-Expert® software. Check it out and search for answers. If you come up empty, do not be shy: Ask your question! Also, this being a forum, we encourage you to weigh in!

For an assortment of appetizers to get this Alert off to a good start, follow this link,* (-> new web site!), and see a number of new blogs (listed below, beginning with the most recent one):

—Misuse of statistics calls into question the credibility of science
—Test and evaluation of the Great Panjandrum — a spectacular failure for weaponry
—Evolutionary operation

*Need a feed or e-mail updates from StatsMadeEasy? Go to It's easy!

"Your StatsMadeEasy blogs brighten up a dreary workday!"
—Applied Statistician, Florida

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

1. FAQ: How do I keep predictions from going beyond 100 percent?
2. Expert FAQ: Why use an I-optimal (vs D-optimal) design?
3. Webinar Alert: Encore presentation of DOE Made Easy and More Powerful via version 8 of Design-Expert Software
4. Support Alert (2nd): Support for V6 of Design-Expert will soon cease — deadline for upgrade discount extended through April
5. Events Alert: European DOE User Meeting (3rd Notice), conferences on biotechnology and statistics in quality
6. Workshop Alert: See when and where to learn about DOE

P.S. Quote for the month: A paradoxical good-luck charm kept by afamous physicist.

(Page down to the end of this ezine to enjoy the actual quote.)


1. FAQ: How do I keep predictions from going beyond 100 percent?

-----Original Question-----
Malaysian student
"In optimization criteria for Design-Expert, I have chosen the goal for my response as 'maximize.' The solution produces a response more than 100% (eg. 104%). This is impossible. What can I do to prevent such a result?"

Answer (from Stat-Ease Consultant Shari Kraber):
"Try re-analyzing your response using the Logit transformation. Since percent is your response, on the Logit transform screen, enter the low limit of 0 and a high limit of 100. This will constrain the response values and may also provide a better analysis. When looking at the model graphs or the optimization, go to Display Options, Responses in Original Scale, to get the graphics back into your original units."

PS. See more details on logit in my very first DOE FAQ Alert in March 2001 (#2) at

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


2. Expert FAQ: Why use an I-optimal (vs D-optimal) design?

-----Original Question-----
Statistician, US Army
"Somebody asked me why I didn't use an IV-optimal design. One clear answer of course is because my tool didn't allow me. However, I see that version 8 of Design-Expert ("DX8") now offers this option for optimal design (in addition to D-optimality). I'm guessing that the design really wouldn't be that different as IV-optimal rather than D. Which approach do you advise?"

Answer (from Stat-Ease Consultants Shari Kraber & Pat Whitcomb):
"The simplest answer to the question of D or IV is that if you are trying to simply detect effects, D-optimality is the best method. However, if you are trying to approximate a response surface with the most overall precision, then IV optimality is the winner.

The differences in designs built one way or the other will depend on the polynomial model they are based on. For example, if you specify a two-factor interaction (2FI) model, both D and IV would force the points to the vertices because those are the necessary points to estimate the model effects. When upgrading the model to quadratic, design points for D vs IV might diverge slightly. However, Design-Expert adds lack-of-fit points and replicates which smooth away many differences between the two types of optimalities, especially for experiments with only a few factors.

For the reasons provided at the outset of this response, D-optimal is the DX8 default for general factorials. The IV-optimal approach is defaulted for response surface methods (RSM) and mixture designs."

(Learn more about optimal design by attending the two-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.)


3. Webinar Alert: Encore presentation of DOE Made Easy and More Powerful via version 8 of Design-Expert Software

Keeping it simple and making it fun, Stat-Ease will introduce an array of statistical methods for design of experiments (DOE) made easy and more powerful via version 8 of Design-Expert software:

—Two-level factorials for process screening, characterization and verification
—Response surface methods (RSM) for process optimization
—Multicomponent mixture design for optimal formulation.

I will encore the first in a series of free webinars by working through case studies on factorial design on Wednesday, April 28 at 10 AM USA Central Time* (CT).

Stat-Ease webinars vary somewhat in length depending on the presenter and the particular session — mainly due to breaks for questions: Plan for 45 minutes to 1.5 hours, with 1 hour being the target median.

When developing these one-hour educational sessions, our presenters often draw valuable material from Stat-Ease DOE workshops. Attendance may be limited, so sign up soon by contacting our Communications Specialist, Karen, via If you can be accommodated, she will
provide immediate confirmation and, in timely fashion, the link with instructions for our new web conferencing vendor: GotoWebinar (see

*(To determine the time in your zone of the world, try using this link: Note that we are based in Minneapolis, which appears on the city list that you must manipulate to calculate the time correctly. It seems that figuring out the clock on international communications is even more complicated than statistics! Good luck!)


4. Support Alert (2nd): Support for V6 of Design-Expert will soon cease — deadline for upgrade discount extended through April

Those of you who still use v6 of Design-Expert — now is the time to make the leap to v8 by taking advantage of the limited-time offer for an economical upgrade. Starting from a listing of "what's new" in v8 at you can trace back all the added features of V7.1 and V7, if you like.

However, think of a small black and white television versus a state-of-art flat-panel high-definition fast-refresh color TV. That is the leap you will achieve by upgrading to Design-Expert version 8. Why hold back on investing in DOE software whose price pales in comparison to the value of more effective experimentation? Go for the top of the line!

With version 6 now three generations behind (it completed development in the late 1990's), it will no longer be fully supported by Stat-Ease programmers and statistical consultants after April 30th (we extended the original deadline of March 31st). Please upgrade your software to continue taking complete advantage of the superb help provided by our professional staff.


5. Events Alert: European DOE User Meeting (3rd Notice), conferences on biotechnology and statistics in quality

The Third European DOE User Meeting will be held June 1-2 in Lucerne, Switzerland, with pre- and post-conference workshops held on May 31 and June 3. It's sponsored by Stat-Ease, CQ Consultancy (Belgium) and Statcon (Germany). Come to increase your understanding of design of experiments (DOE) techniques, learn of successful real-life applications of DOE, and also attend presentations specific to Stat-Ease software and its features. For details, see

Stop by the Stat-Ease exhibit at the American Association of Pharmaceutical Scientist's (AAPS) National Biotechnology Conference (NBC) in San Francisco, on May 17-18. For details see Pat Whitcomb and I will host a session on "Advancements in Mixture Design" at the Joint Research Conference (JRC) on Statistics in Quality, Industry, and Technology in Gaithersburg, MD on May 25. Three talks will be presented:

—State-of-the-Art Tools for Designing Mixture Experiments, by Pat Whitcomb and Mark J. Anderson, Stat-Ease Inc.
—Model-Robust Mixture Experiment Designs, by Greg F. Piepel, Pacific Northwest National Laboratory
—Mining Mixture Data to Find the Most Reliable Prediction Model, by Dean V. Neubauer, Corning Inc./RIT

See for all the conference details.

Click for a list of upcoming 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.


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

Seats are filling fast for the following DOE classes. If possible, enroll at least 4 weeks prior to the date so your place can be assured. However, do not hesitate to ask whether seats remain on classes that are fast approaching! Also, take advantage of a $395 discount when you take two complementary workshops that are offered on consecutive days.

—> Experiment Design Made Easy (EDME)
(Detailed at
> April 27-28 (Minneapolis, MN)

—> Response Surface Methods for Process Optimization (RSM)
> April 29-30 (Minneapolis)

(Take both EDME and RSM to earn $395 off on combined tuition.)

—> Designed Experiments for Life Sciences (DELS)
> May 10-11, 2010 (San Diego,* CA)
*New location!

—> Mixture Design for Optimal Formulations (MIX)
> May 18-19 (Minneapolis)

--> Advanced Formulations: Combining Mixture & Process Variables
(MIX2) (
> May 20-21 (Minneapolis)

(Take both MIX and MIX2 to earn $395 off on combined tuition.)

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. Quote for the month—A paradoxical good-luck charm kept by a famous physicist:

"Neils Bohr was said to have had a horseshoe hanging over his office door for good luck. When asked how a physicist could believe in such things, he said, 'I am told it works even if you don't believe in it."

—Kevin Meyer, "Evolving Excellence" blogger

Trademarks: Stat-Ease, Design-Ease, Design-Expert and Statistics Made Easy 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, Wayne Adams and Brooks Henderson (see for resumes)
—Statistical advisor to Stat-Ease: Dr. Gary Oehlert (
—Stat-Ease programmers, led by Neal Vaughn and Tryg Helseth (
—Heidi Hansel Wolfe, Stat-Ease marketing director, Karen Dulski, and all the remaining staff that provide such supreme support!


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, #7-11 Nov 07, #7-12 Dec 07, #8-1 Jan 08, #8-2 Feb 08, #8-3 Mar 08, #8-4 Apr 08, #8-5 May 08, #8-6 June 08, #8-7 July 08, #8-8 Aug 08, #8-9 Sep 08, #8-10 Oct 08, #8-11 Nov 08, #8-12 Dec 08, #9-01 Jan 09, #9-02 Feb 09, #9-03 Mar 09, #9-04 Apr 09, #9-05 May 09, #9-06 June 09, #9-07 July 09, #9-08 Aug 09, #9-09 Sep 09, #9-10 Oct 09, #9-11 Nov 09, #9-12 Dec 09, #10-1 Jan 10, #10-2 Feb 10, #10-3 Mar 10 , #10-4 Apr 10 (see above)

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