Issue: Volume 7, Number 12
Date: December 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 (beginning with the most recent on down):
— Extrapolating beyond...where you have a leg to stand on
— Statisticks (sic)
— A laugher of a curve offers a lesson on leverage
— Why experiment?

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

1. FAQ: Why two-level factorial design trumps "OFAT"
2. Software Review: Scientific Computing World declares v7.1 of Design Expert® software "a very worthwhile upgrade"
3. Reader Response: Accolades for 2nd Edition of DOE Simplified
4. Info Alert: Publish your DOE success story!
5. Event Alerts: Do you seek a speaker on DOE?
6. Workshop Alert: Experiment Design Made Easy in San Diego

PS. Quote for the month: Can statistics be glamorous? (Page through to the end of this e-mail to enjoy the actual quote.)


1. FAQ: Why two-level factorial design trumps "OFAT"

-----Original Message-----
From: Chicago
"Thank you for a well presented and truly useful book [DOE Simplified]. You have easily surpassed the 'fitness for use' criteria as Juran defined 'quality.' Since you probably get a lot of e-mails, I'll keep this brief: You describe an experiment with three factors that would take 16 OFAT [one factor at a time] runs but only 8 DOE runs.* The DOE runs make perfect sense but I am having difficulty coming up with the 16 necessary trials using the OFAT approach. No matter what I do, I'm not coming up with 16. I am a PMP [Project Management Professional] certified project manager and need to show this difference to a PM class I am teaching."

*(See Figure 1 in "Trimming the FAT out of Experimental Methods" posted at

First of all, thanks for the kind comments about the book. :) To make the case on efficiency of two-level factorial design versus OFAT, you must first get agreement from your class that the more data one collects the better — specifically that the power of averaging increases with the number of runs. For example, an average computed from 4 runs will provide a more precise result than a single run. I would be very surprised if any of your PM students disagree with this basic premise. Now take a look at the two-level design for three factors that forms the cube. Notice that there are 4 points at the each level of factor A (right vs left sides of the cube). Thus the effect of A is based on averages of 4 runs each. Therefore, to achieve the same power of estimation, OFAT must make 4 runs at the high level of A and the low (the origin). This argument also rules for calculating effects of B and C:They, too, must be run 4 times high in OFAT for this old-fashioned experimental method to match the power of two-level factorial design. Finally, simply count up the dots — 8 in the cube versus 16 for OFAT.

PS. For first-hand testimonial on the value (50 million dollars!!!) of two-level factorial design versus OFAT, see item #3 at It tells the story of how Chevron's senior statistician Jake Sredni proposed a two-level fractional factorial design that subsequently saved the
company $50,000,000 in raw material costs. Prior experimentation via OFAT went nowhere according to the chemical engineer (Gary Knapp) who passed along this anecdote to me.

(Learn more about two-level factorial design 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.)


2. Software Review: Scientific Computing World declares version 7.1 of Design Expert® software "a very worthwhile upgrade"

In a recent review for Scientific Computing World, writer Felix Grant finds that Design Expert 7.1 "builds on the many improvements from earlier upgrades." See his evaluation at (shortened from original link to page posted at Felix concludes by declaring v7.1 "a very worthwhile upgrade." If you own v7.0 or an older version, contact Stat-Ease Customer
Service via to get a quote on upgrading your Design-Expert or Design-Ease® software. Give one of these leading-edge DOE programs a try by downloading a fully-functional copy from


3. Reader Response: Accolades for 2nd Edition of DOE Simplified

I am always pleased to get positive feedback like this from a university Professor of Chemical and Biochemical Engineering: "I congratulate you both on co-authoring such an amazing book, DOE Simplified.* Truly, you have simplified complex concepts and presented them in the most logical manner. I thoroughly enjoyed reading through the sections of your book. You have left out all the unnecessary math and conveyed the principles in the most effective way." The DOE, and subsequently RSM, Simplified books* were intended as primers for experimenters with little or no statistics background. They have served this purpose — no doubt. However, I did not anticipate the number of engineering schools who appreciate our practical approach to these statistical tools.

*(The two-part series of "Simplified" books on DOE and RSM can be ordered online from


4. Info Alert: Publish your DOE success story!

Stat-Ease is searching for individuals or teams willing to share their success stories. Inspirational case-study articles are highly sought after in all industries. Anyone who has designed an experiment that has led to improvements in their products or processes is invited to contact us. Don't worry if it didn't go perfectly, as long as you learned something about the subject of interest. Perhaps you saved the company some money, or were able to make a product that met or surpassed customer requirements. We can team you up with a technical writer who will coordinate the creation of the magazine article. You provide the interesting information and the technical writer provides the format. Plus, the technical writer does the work of submitting your case study to the appropriate magazines or journals. The article is published with your name as author.

If you are interested in publishing your story, please contact Heidi via or call her at 612.746.2033.

See our current collection of DOE case studies and articles at Factor details can be coded for secrecy sake, so confidentiality need not be compromised.

"Another company had end-users completely locked up. Before the story* ran, those users didn't know we even existed. We gained ten new clients — a very significant number in this small market." — Jennifer Borkovich, Engineer

*"Design of Experiments Increase Hot-Ink Roller Impressions (and Perceptions)" published in the May 2000 issue of American Ink Maker and in a web exclusive for PCI Magazine.

(Jennifer was quoted by technical writer Richard Burnham in an inspiring and informative article "Engineers as Credible Marketers" published by The Business to Business Marketer — see


5. Events Alert: Do you seek a speaker on DOE?

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.

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


6. Workshop alert: Experiment Design Made Easy in San Diego Seats are filling fast for the following DOE classes

Seats are filling fast for the following DOE classes:

—> Experiment Design Made Easy (EDME)
(Detailed at
> January 22-24 (San Diego, CA)

—> Mixture Design for Optimal Formulations (MIX)
> January 29-31 (Minneapolis)

—> Response Surface Methods for Process Optimization (RSM)
> February 26-28 (Minneapolis)

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—Can statistics be glamorous:

"Glamor is the art of giving the illusion that you can do something well and that you are worth doing it with — without ever descending to the crudity of showing how you do it. The opposite of glamor is statistics."
—Attributed to a professor of nondramatic Renaissance literature (from Chance magazine)

PPS. Hmmm, so is 'nondramatic' literature glamorous?
"More matter with less art."
Shakespeare, Hamlet, act 2, scene 2

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, #7-11 Nov 07, #7-12 Dec 07 (see above)

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