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Issue:
Volume 8, Number 6
Date:
June 2008
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 http://www.statease.com/doealertreg.html. If this newsletter prompts you to ask your own questions about DOE, please address them via mail to:[email protected].
For an assortment of appetizers to get this Alert off to a good
start, see these new blogs at http://statsmadeeasy.net (beginning with the most recent one):
— GPA mongers lose out to students willing to take on tougher classes
— Advice from famous physicist Feynman: "You must not fool yourself"
— Duck named DOE (pronounced "dewie")
— What would Deming say about the demise of testing in education? (Also see comment by "Curious Cat*" the nom de plume for John Hunter, son of statistical guru Bill.)
— Baseball batting averages throw some curves at statisticians (See comment also.)
Also check out the thoughtful feedback to this prior blog:
— Could a butterfly in Brazil cause a twister in Texas? (2 comments, so far).
* http://management.curiouscatblog.net/
Topics in the body text of this DOE FAQ Alert are headlined
below (the "Expert" ones, if any, delve into statistical details).
1. FAQ: Re-analyzing a categoric factor as numeric
2. FAQ: What is the applied use of "Corrected Total" in the analysis of variance (ANOVA) table?
3. Book giveaway (US/Canada only): Enter drawing for 3 copies of "Engineering Statistics, 3rd Ed" by Montgomery, Runger, Hubele
4. Info alert: Tabletop hockey meets goals for teaching experimental design — published by ASQ Statistics Division
5. Webinar alert: Dual Response Surface Methods (RSM) to Make Processes More Robust
6. Events alert: See where and when you can hear from Stat-Ease
7. Workshop alert: "Experiment Design Made Easy" in San Francisco
8. New course offered: Stat-Ease unveils "Designed Experiments for Life Sciences" later this summer — enrollment now open
P.S. Quote for the month: Ecolab statistician Bruce White's wistful thinking on the inevitable demise of people in his profession. (Page
through to the end of this e-mail to enjoy the actual quote.)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1. FAQ: Re-analyzing a categoric factor as numeric
-----Original Question-----
From: New York
"In reference to the General Factorial Tutorial for Design-Expert® software,* the example of the temperature and material type considered the factors categorically. The question I have is that if I were to run similar experiments using temperature as a continuous factor, how I can specify this to the software. Your help in this matter is greatly appreciated."
* http://www.statease.com/x71ug/DX71-02C-Gen2Factorial-P1.pdf
Answer (from Stat-Ease Consultant Wayne Adams):
"Once a design has been created such as the battery example, you can make a factor numeric by right-clicking on the top of the factor and selecting the option to Make Numeric. Next, right-click the response column, select Edit Info and press the advance option button to "analyze as polynomial." Design-Expert then activates its features for response surface methods (RSM). If there are three levels in the now numeric factor, then a quadratic model can be fit.**
The purpose of the battery design was to figure out what material worked best across a range of temperatures. In other words what material produced the longest battery life in any temperature condition.
The difference between a factorial (categoric) and a response surface (numeric) is the form of the question they are intended to answer. Factorial designs answer the question, 'What factors have an impact on the response?' Response surface designs answer the question, 'What is the best polynomial model for the data?
Luckily, designed experiments can often answer both questions."
** See http://www.statease.com/x71ug/DX71-02D-Gen2Factorial-P2.pdf
for more details.
—Mark
(Learn more about polynomial modeling by attending the three-day computer-intensive workshop "Response Surface Methods for Process Optimization." See http://www.statease.com/clas_rsm.html for a description of this class and then link from this page to the course outline and schedule. Then, if you like, enroll online.)
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2. FAQ: What is the applied use of "Corrected Total Sum of Squares" in the analysis of variance (ANOVA) table?
-----Original Question-----
From: UK
"The ANOVA tables in 'DOE Simplified'* contain the row "Cor Total" [Corrected Total Sum of Squares]. I understand where you get the numbers, but I do not see where it is used. What is the applied use of 'Cor Total'?"
*"DOE Simplified: Practical Tools for Effective Experimentation" by Anderson (me) and Whitcomb (my colleague Pat) is now in 2nd edition (2007). See http://www.statease.com/doe_simp.html for details and a link to online purchasing.
Answer:
Here's my 'take.' Back in the days of Fisher — the inventor of analysis of variance (ANOVA), "calculators" were people his organization (Rothamsted Experimental Station, UK) hired to add and subtract numbers.** Then the corrected total sum of squares (adjusted for the mean) was useful as a check sum on the calculations. It does not have much use per se, unless you really want to know the total amount of variation that occurs with the individual observations of response about the mean. However, it does come into play for statistics such as R-squared.
P.S. to statisticians out there: Feel free to weigh in on this by sending me an e-mail.
**In later years, Fisher took advantage of electro-mechanical calculators as pictured at this web site by Monash University http://www.csse.monash.edu.au/~lloyd/tildeImages/People/Fisher.RA/ Check out their "millionaire" calculator. Thank goodness for modern day computers and dedicated DOE software!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3. Book giveaway (US/Canada only): Enter drawing for 3 copies of "Engineering Statistics, 3rd Ed" by Montgomery, Runger, Hubele
(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 June 13 if you'd like to enter a drawing for a free copy of "Engineering Statistics, 3rd Ed" by Montgomery, Runger, Hubele. We have 3 of this older edition, originally priced at $150, to move along to good homes for those wanting to augment their shelf of quality books.
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.
(Learn more about engineering statistics by attending the two-day computer-intensive [Microsoft Excel] workshop "Statistics for Technical Professionals." For a description of this class — offered on-site only, see http://www.statease.com/clas_stp.html. For more information, call Elicia at 612.746.2038.)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4. Info alert: Tabletop hockey meets goals for teaching experimental design — published by ASQ Statistics Division
Brian Sersion, editor of the Statistics Division Newsletter in which this article was published (Volume 26, No. 3 Spring 2008) says "It’s time for some hockey! As the Stanley Cup season enters full swing, or should I say full body check, we have a terrific design of experiments Mini Paper for your reading pleasure. Mark
Anderson describes an in-class experiment that illustrates the power of two-level factorial design. As a bonus you can learn how to shoot a wicked slap shot!" See my original manuscript at http://www.statease.com/pubs/hockey.pdf and/or its publication via the Statistics Division archive of newsletters at http://www.asqstatdiv.org/newsletterarch.php — a treasure trove of mini-papers on useful tools. If you are not already a member, you should consider joining — they invite you at
http://www.asqstatdiv.org/membership.htm.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5. Webinar Alert: Dual Response Surface Methods (RSM) to Make Processes More Robust
You are invited to attend a free web conference by Stat-Ease on "Dual Response Surface Methods (RSM) to Make Processes More Robust" on Tuesday, July 1 at 8 AM, USA Central Daylight Time (CDT), which is 13:00 in Coordinated Universal Time (UTC). (We are at UTC -5 under CDT.) It will be offered again at 8 PM that evening (01:00 UTC July 2 — Wednesday*) and one more time the following day at 12 PM noon (07:00 UTC July 2). This talk, which I will present, is described below:
"Response surface methods (RSM) provide statistically-validated predictive models, sometimes referred to as "transfer functions," that can then be manipulated for finding optimal process configurations. The dual response approach to RSM captures both the average and standard deviation of the output(s) and simultaneously optimizes for the desired level at minimal variation, thus achieving an on-target, robust process. With inspiration provided by a case study on a semiconductor etching process, the positive repercussions of these methods will be readily apparent, especially for those involved in design for six
sigma (DFSS) quality programs."
When developing these educational sessions, our presenters often draw valuable material from Stat-Ease DOE workshops. Attendance may be limited for these three one-hour webinar sessions. Contact
our Communications Specialist, Karen, via [email protected] to sign up. If you can be accommodated, she will send you the link for the WebConnect and dial-in for ConferenceNow voice via telephone. Toll-free access extends worldwide, but not to all countries.
*This is a trial run to see whether we can better serve our Far East clients. For example (if I've done my time calculations correctly!), the second webinar session will be at:
11 AM in Melbourne (Australian EST, +15 hours)
10 AM in Tokyo (+14 hours)
9 AM in Shanghai (+13 hours)
8 AM in Bangkok (+12 hours)
6:30 AM in Mumbai.(+10.5 hours)
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6. Events alert: See where and when you can hear from Stat-Ease
Click http://www.statease.com/events.html 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. Contact [email protected] if you have an event coming up with an open slot for a presentation.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7. Workshop alert: "Experiment Design Made Easy" in San Francisco
—> Experiment Design Made Easy (EDME)
(Detailed at http://www.statease.com/clas_edme.html)
> July 8-10 (San Francisco, CA)
> August 19-21 (Minneapolis, MN)
—> Mixture Design for Optimal Formulations (MIX)
(http://www.statease.com/clas_mix.html)
> June 10-12 (Minneapolis)
> July 29-31 (Minneapolis)
—> Response Surface Methods for Process Optimization (RSM)
(http://www.statease.com/clas_rsm.html)
> September 23-25 (Minneapolis)
—> DOE for DFSS: Variation by Design (DDFSS)
(http://www.statease.com/clas_ddfss.html)
> November 11-12 (Minneapolis)
See http://www.statease.com/clas_pub.html 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 mailto:[email protected].
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8. New course offered: Stat-Ease unveils "Designed Experiments for Life Sciences" later this summer — enrollment now open
Stat-Ease announces its newest workshop — "Designed Experiments for Life Sciences" (DELS), a three-day workshop aimed at researchers in pharma, biopharma, diagnostic, medical device, etc. Enroll now for the inaugural presentation on August 5-7 in our Minneapolis training center. Call Elicia at 612.746.2038 for
details.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I hope you learned something from this
issue. Address your general questions and comments to me at: [email protected].
PLEASE DO NOT SEND ME REQUESTS TO SUBSCRIBE OR UNSUBSCRIBE — FOLLOW THE INSTRUCTIONS AT THE END OF THIS MESSAGE.
Sincerely,
Mark
Mark J. Anderson, PE, CQE
Principal, Stat-Ease, Inc. (http://www.statease.com)
2021 East Hennepin Avenue, Suite 480
Minneapolis, Minnesota 55413 USA
PS. Quote for the month —Ecolab statistician Bruce White's wistful thinking on the inevitable demise of people in his profession:
"Old statisticians never die — they just lose their significance"
—Ecolab's Bruce White (although others may have expressed similar thoughts on mortality).
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 and Wayne Adams
(see http://www.statease.com/consult.html
for resumes)
—Statistical advisor to Stat-Ease: Dr. Gary Oehlert (http://www.statease.com/garyoehl.html)
—Stat-Ease programmers, especially Tryg Helseth and Neal Vaughn
(http://www.statease.com/pgmstaff.html)
—Heidi Hansel, Stat-Ease marketing director, and all the remaining
staff
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