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Vol: 10 | No: 12 | Dec 2010
The DOE FAQ Alert
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, click here.

Feel free to forward this newsletter to your colleagues. They can subscribe by going to this registration page.

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.

Also, Stat-Ease offers an interactive website—The Support Forum for Experiment Design. 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 to Design-Ease® and Design-Expert® software. Check it out and search for answers. Also, this being a forum, we encourage you to weigh in!
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This months topics:

  If this newsletter prompts you to ask your own questions about DOE, please address them via e-mail to:


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: December issue of the Stat-Teaser details a DOE on how to keep the heat in a cup of tea—‘tis the season for warm beverages!
2:  FAQ: How to handle constraints on a mixture experiment via optimal design
3:  Webinar Alert: DOE Made Easy and More Powerful via Design-Expert Software, Part Three—Multicomponent Mixture Design for Optimal Formulation
4:  Workshop Alert: See when and where to learn about DOE
PS. Quote for the month:
Counting our blessings.

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1: Newsletter Alert:

The December issue of the Stat-Teaser details a DOE on how to keep the heat in a cup of tea—‘tis the season for warm beverages!

Many of you have received, or soon will, 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 this link.  It features a DOE that tested a claim by an insulated-mug maker that they “Keep Hot Drinks Hotter & Cold Drinks Colder Longer.”

This Stat-Teaser also provides a heads-up by me on “What is Mixture Design and What's In It for You?”

Thank you for reading our Stat-Teaser newsletter.  If you get the hard copy, but find it just as convenient to read what we post to the Internet, consider contacting us to be taken off our mailing list, thus conserving resources.  (Note: You will be notified via the DOE FAQ Alert on new newsletter posts.)  In any case, we appreciate you passing along hard copies and/or the link to the posting of the Stat-Teaser to your colleagues.

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2: FAQ: How to handle constraints on a mixture experiment via optimal design

Original Question:

From a Chemical engineer:
"I recently came across an informative detailing of “Mixture and mixture process variable experiments for pharmaceutical applications” by Christine Anderson-Cook, Heidi Goldfarb, Connie Borror, Douglas Montgomery, et al in Pharmaceutical Statistics (Oct/Dec 2004, Vol. 3, Issue 4, pp 247-260).  Therein, an example of the use of Design-Expert software is given, where the mixture investigated is of three excipients that must make up 75% of a formulation (the active is fixed at 25%).  I am trying to use Design-Expert the same way, but I am unable to include the said constraint (using the simplex centroid design).  I am not sure I can see the option for a D-optimal design (referred to by the authors)."


From Stat-Ease Consultant Shari Kraber:
"A simplex centroid (or lattice) design can only be used when all components have the same range.  So when we have constraints (the majority of the cases), an optimal design must be used.  If you have updated to version 8 of Design-Expert,* then the option on the Mixture tab is simply called “Optimal” now, because we have expanded the types of optimal designs available. The new default for response surface and mixture designs is I-V optimal, but D is still an option on the drop-down list for “Optimality."

(Learn more about component constraints by attending the two-day computer-intensive workshop "Mixture Design for Optimal Formulations." Click on the title for a complete description and link from this page to the course outline and schedule. Then, if you like, enroll online.)

*Version 8.0.4 of Design-Expert(R) software is posted here for free trial evaluation.  This web site also provides free patches to update older licensed versions of 8.0.  If you haven't upgraded to v8 yet, click here to learn what you're missing.  Version 8 offers many useful features for design (such as I-V optimality) and analysis, as well as nicer-looking and more functional graphics.  Why short yourself?

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3: Webinar alert: DOE Made Easy and More Powerful via Design-Expert Software, Part Three—Multicomponent Mixture Design for Optimal Formulation

Keeping it simple and making it fun, Stat-Ease is introducing 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 present an encore of the third of this series of free webinars by working through case studies on mixture experiments on Wednesday, January 27th at 10:30 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 Dulski, 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.

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

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4: 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 up to a $395 discount when you take two complementary workshops that are offered on consecutive days.

All classes listed below will be held at the Stat-Ease training center in Minneapolis unless otherwise noted.

See this link to a listing of upcoming classes 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

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  Please do not send me requests to subscribe or unsubscribe—follow the instructions at the very end of this message. 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.

PS. Quote for the month—Counting our blessings:


The hardest arithmetic to master is that which enables us to count our blessings.”

—Eric Hoffer

Season’s greetings! MJA

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
—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!

DOE FAQ Alert ©2010 Stat-Ease, Inc.
All rights reserved