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Vol: 12 | No: 4 | Jul/Aug'12
The DOE FAQ Alert

Heads-up (below!)
Monkee supports Hacker’s position that math education is unnecessary

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.

TIP: Get immediate answers to questions about DOE via the Search feature on the main menu of the Stat-Ease® web site. This pores not only 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 this registration page.

Also, Stat-Ease offers an interactive web site—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 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 with answers! The following Support Forum topic provides a sampling of threads that developed since my last Alert:

  • Area: Design Selection, Topic: “Help with power/FDS with non-sequential CCD”, Question: “With a single rep of factorial points my power estimates for ME and 2FI vary from high 40%s to low 70%s. My quadratic estimates are mid to high 90%s. I know that FDS is a more appropriate prediction diagnostic for RSM, and for that I'm getting really great results for my d/s ratio, but should I be looking at power for my ME and 2FI?”

To open yet another avenue of communications with fellow DOE aficionados, sign up for The Stat-Ease Professional Network on Linked In and start or participate in discussions with other software users. A recent thread features “Using simulations with DOE. How do you interpret and introduce pure error?

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Topics discussed since the last issue of the DOE FAQ Alert (latest one first):

Please do not be shy about adding your take about any news or views you see in StatsMadeEasy.  Thanks for paying attention.



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:  Training resource alert: New web-based ‘launch pad’ for DOE Simplified self-study
2:  FAQ: For teaching purposes, creating a workable simulation that requires an inverse transformation
3:  Info alert: Superb text on DOE available free under Creative Commons License
4:  Book giveaway: Feeling lucky? Put your name in for a free DOE text. (Do it anyway!)
5:  Reader contribution: Free DOE simulator app for iPhone
6:  Events alert: ENBIS Slovenia, QbD India, Glass Cincinnati, FTC Saint Louis
7:  Workshop alert: See when and where to learn about DOE

PS. Quote for the month: Monkees band member supports Hacker’s position that math ed is unnecessary.

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1: Training resource alert: New web-based ‘launch pad’ for DOE Simplified self-study

I am pleased to announce a new ‘launch pad’ for DOE Simplified self-study—a voiced-over slide presentation on foundational statistics (mean, standard deviation, confidence interval, normal plot, F-test), simple comparative experiments and two-level factorial designs.  This is intended as an educational aid for those who, for one reason or another, cannot make their way to a live lecture (far preferable!).

I recorded and then produced* a dozen short videos in MP4 format that cover the first three chapters of the DOE Simplified book.  After completing the 2½ hours or so of my presentation, plus off-line time on assignments, students will then be expected to complete the book on their own.

Those who’ve provided evidence of participation by their submission of homework, questions and a completion of a rudimentary final exam will be issued 1 Continuing Education Unit (CEU).  More importantly, they will come to appreciate the value of multifactor testing and gain a working knowledge of the methodology, thus putting them far up the power curve for their work in research and development, process engineering and the like.  There is no substitute for a multiday workshop on this statistical tool, but the DOE Simplified distance-based learning suite—a blend of web-based presentation, off-line reading and homework—can be taken anywhere at any time by anyone with the need to know.

Eventually I expect that Stat-Ease will charge tuition for taking this course on DOE.  However, for a limited time it will be provided selectively on request for piloting purposes.  For those who are already well-versed in DOE, but know someone who might benefit by learning about this tool, feel free to recommend this to them.  However, due to demands on my time and my Stat Help colleagues who will also pitch in for the evaluation of feedback and answering questions, I can only accommodate limited numbers for the time being.

*(Using Camtasia Studio in conjunction with Microsoft Powerpoint.)

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2: FAQ: For teaching purposes, creating a workable simulation that requires an inverse transformation

Original Question:

From a Statistical Educator:
“I have a question about something I recently did in Design-Expert V8.  I used the response simulation tool to create a model for a design (second-order) and tried to make the problem such that a 1/y transformation would be required.  When I analyzed the data there was no indication that a transformation was necessary.  In fact, all the models I produced were ugly, and it didn’t matter what transformation (or none) I used."

Simulation Transfrom Screen
Simulation Transform Screen

Around the same time I did something similar using a log transformation and that worked perfectly.  I thought perhaps I had picked a model where the range of the responses was so small that transformations wouldn’t help, but I don’t think that’s the case.  Any ideas?”


From Stat-Ease Consultant Pat Whitcomb:
“Re-open your ‘sim’ file by pressing the button at the dialog box found via main menu Design Tools, Simulation Editor.

Simulation Editor
Simulation Editor

It now generates both negative and positive responses from the factor levels you’ve applied.  The inverse transform will not work on data like this due to it blowing up at the zero value.  All negative or all positive response values are OK.  So in your simulation model simply add enough to the intercept to avoid negative responses.  Then everything works just fine—this becomes, as you’d hoped, a good practice-problem to illustrate via simulated data the need for an inverse transformation.”

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

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3: Info alert: Superb text on DOE available free under Creative Commons License

A First Course in Design and Analysis of Experiments by Gary W. Oehlert, first published in 2000 by W. H. Freeman, is now being distributed under a Creative Commons License via this link.  Reviewer Shaun S. Wulff says, “This text is written for statisticians and non-statisticians alike… Given the readability, the use of relevant examples, and the practical approach to design and analysis, this text is a valuable reference for a first course in experimentation.”*  I recommend you bookmark this in your Internet favorites.  (Full disclosure: Professor Oehlert is our Advisor.)

*(The American Statistician, Volume 57, Issue 1, 2003, pages 66-67.)

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4: Book giveaway: Feeling lucky? Put your name in for a free DOE text. (Do it anyway!)

(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 September 7 if you’d like a free DOE text.  I’ve been collecting old, but golden, DOE books for about a year now.  It’s time to find them a better home.  Here’s what is up for grabs:

    1. Two worn, but serviceable, Design and Analysis of Experiments: 4th Edition by Doug Montgomery—these provide all the basics of DOE,
    2. A slightly used DOE Simplified book, signed by the authors (me and Pat), from exhibits at technical conferences,
    3. A new RSM Simplified book, signed by the two of us, from the latest printing by CRC Press (Taylor & Francis Group).

(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.)

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5: Reader contribution: Free DOE simulator app for iPhone

Dr. Leonard Lye, Professor of Civil Engineering Memorial University of Newfoundland, says “My DOE-SIM app with three simulators is now available for the iPhone in the App store.  It is free, just go to the App store and search for it, then tap to see details and download.  A ten-simulator version DOE-SIM Pro is now available for $3.99.  It works both on iPhone and iPad.

Stat-Ease Consultant Brooks Henderson says. “I downloaded the app and it works fine on my iPhone 4S.  I tried all 3 simulators out and a few settings and they seem to work well.  I like the fact that the experiment takes a little longer when you choose the high level of time for the popcorn experiment as opposed to the low level (nice touch).  I also like the instructions giving the goal of the experiment and some questions to answer."

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6: Events alert: ENBIS Slovenia, QbD India, Glass Cincinnati, FTC Saint Louis

Pat Whitcomb reveals “How to Design Experiments when Categoric Mixture Components Go to Zero” at the 12th Annual Conference of the European Network for Business and Industrial Statistics (ENBIS) Slovenia on September 9-13.  See conference details here.

Stat-Ease Consultant Brooks Henderson returns to India for an encore of “Overview of DOE for QbD” at the Quality by Design Conference in Ahmedabad September 24-26.  For more information, follow this link.

I will teach “Design of Experiments Simplified” on October 1 at the Glass Problems Conference in Cincinnati, Ohio that week.  See more here.

Pat will present a one-day short course on “DOE Tools to Combine Mixture and Process Variables” on Saturday, October 6 following the 2012 Fall Technical Conference (FTC) in Saint Louis, Missouri.  Follow this link to all the details, including the time when Pat will present an encore on “How to Design Experiments when Categoric Mixture Components Go to Zero” to this American audience.

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

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7: 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.

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

* Take both EDME and RSM in February to earn $395 off the combined tuition!

** Take both MIX and MIX2 to earn $395 off the combined tuition!

See this web page 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.
2021 East Hennepin Avenue, Suite 480
Minneapolis, Minnesota 55413 USA

PS. Quote for the month—Monkees band member supports Hacker’s position that math ed is unnecessary:

Forcing me to learn school-taught algebra was like trying to teach a lion table manners.”

—The Monkees band member Michael Nesmith supporting Hacker’s questioning the need for teaching math. See a StatsMadeEasy blog on this and an unrepentant follow-up here.

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
—Heidi Hansel Wolfe, Stat-Ease marketing director, Karen Dulski, and all the remaining staff that provide such supreme support!

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