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 http://www.statease.com/doealertreg.html. If this newsletter prompts you to ask your own questions about DOE, please address them via mail to:StatHelp@StatEase.com.
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):
Also check out the thoughtful feedback to this prior blog:
Topics in the body text of this DOE FAQ Alert are headlined below (the "Expert" ones, if any, delve into statistical details).
1. Released: Version 7.1.4 of Design-Ease® software
PS. Quote for the month: Inventor of DOE suggests alternative to
one question at a time for prying secrets loose from nature. (Page
through to the end of this e-mail to enjoy the actual quote.)
1. Released: Version 7.1.4 of Design-Ease software
A free, fully-functional Design-Ease ("DE") software version 7.1.4 download is now posted at http://www.statease.com/soft_ftp.html for evaluation.* This web site also provides free patches to update older, licensed, versions of 7.1. The new release primarily addresses maintenance issues. View the ReadMe file for installation tips,** known 'bugs,' change history, and FAQs.
Design-Expert® ("DX") software achieved release of V7.1.4 earlier, as announced in last month's DOE FAQ Alert. According to our user database, many V6 licensees have not taken advantage of favorable pricing for the tremendous upgrades developed by Stat-Ease over the last 8 years (DX6 came out around 2000). See http://www.statease.com/dx71descr.html for a detailing on most of the new features (too many to list exhaustively!).
*If you cannot download the software due to organizational security, consider taking the "online tour" to see how easy Stat-Ease software makes the design and analysis of experiments, specifically two-level factorials for discovery or verification.
**Network administrators are advised of some important changes
that must be understood before updating to V7.1.4.
2. FAQ: How do I pick the factors for my experiment?
This is the beginning of a proven strategy for iterative experimentation that is detailed at: http://www.statease.com/pubs/rsmsimpexcerpts--chap1.pdf.
(Learn more about the basics of DOE by studying "DOE Simplified: Practical Tools for Effective Experimentation, 2nd Edition" by Mark J. Anderson & Patrick J. Whitcomb. See its description at http://www.statease.com/doe_simp.html. Intended as a do-it-yourself primer for industrial experimenters, this soft-cover book has become an integral part of many Six Sigma short courses and found a home at a number of colleges, particularly for engineering. It comes with a fully-functional, educational version of Design-Ease version 7.1 software that operates for 180 days on any given personal computer. A network version can be purchased for computer classrooms. For a quote, contact Mailto:firstname.lastname@example.org.)
3. Expert-FAQ: How to combine components in a mixture design and
when it may be appropriate to do so
However, being a chemical engineer by profession, I naturally
fear that combining components only on the basis of their similar
effects might be an oversimplification. The one time I did take
advantage of the combine-components feature of our software was
when experimenting on two flours that showed little impact,
relatively speaking, on taste on a pound-cake recipe I
experimented on at home. For presentation purposes, it made things
easier in the end to combine these two components so I could focus
In conclusion, if I were you, I would check back with the subject-matter expert for this experiment (presuming you are providing stat help and not actually doing the research). Do they say these two components are physically alike? If so, I’d go ahead and combine them for simplicity in analysis and modeling.
*This pays homage to the inventor of DOE, Sir Ronald Fisher, who illustrated basic principals in his story about a Lady tasting tea who claimed the ability to tell whether milk was added to tea, or tea poured into milk. See my alert #4 in the DOE FAQ Alert from July 2004 posted at http://www.statease.com/news/faqalert4-7.html for the outcome of Fisher's verification study on this remarkable claim of the tea-loving Lady.
(Learn more about mixture design by attending the three-day computer-intensive workshop "Mixture Design for Optimal Formulations." For a complete description of this class, see http://www.statease.com/clas_mix.html. Link from this page to the course outline and schedule. Then, if you like, enroll online.)
4. Webinar alert (2nd one): Learn how to accomplish multiple
response optimization with Design-Expert
You are invited to attend a free web conference by Stat-Ease on "Multiple response optimization with Design-Expert" at 8 AM in the Central USA Time Zone on Tuesday, April 1. It will be presented again at 12 PM (noon) on Wednesday, April 2. Here is the abstract from the talk's author, Consultant Shari Kraber:
"The optimization module in Design-Expert searches for combinations of factor levels that simultaneously satisfy the requirements placed on each of the responses and factors. Discover how to get the most out of the optimization module in order to find the "sweet spot" for your product or an operating window for your process. Learn how to fine-tune your search by adding weights and importance settings to your basic criteria. A case study will be used to illustrate all the features of Design-Expert's optimization module."
Attendance may be limited for one or both of these two one-hour webinar sessions. Contact our Communications Specialist, Karen Dulski, via mailto:email@example.com 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.
5. Webinar Q&A (follow up from February's talk on "10 Ways to
Mess Up an Experiment & 8 Ways to Clean It Up")*:
I encourage blocking if the design is stout enough to absorb the price in degrees of freedom. It often removes variations so large that they would otherwise overwhelm important effects.
* The Powerpoint slides from prior webinars are posted at http://www.statease.com/webinar.html. Over 100 attendees enrolled for the most recent presentation on "10 Ways to Mess Up an Experiment & 8 Ways to Clean It Up." This basic-level presentation provided practical advice for actual experimenters. The prior presentations by Consultant Pat Whitcomb provided more advanced statistical details on sizing designs for process screening and mixture optimization. The upcoming webinar by Shari Kraber will be aimed at an intermediate level of expertise on DOE.
6. Events alert: European DOE User Meeting, Biomedical Focus in
The Second European DOE User Meeting will be held March 10-12 in
Berlin, 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 more information, see
See Stat-Ease exhibiting at the 2008 Biomedical Focus Conference in Brooklyn Center, Minnesota on March 17. On the following day, the 18th of March, Stat-Ease Consultant Pat Whitcomb will present a workshop on "DOE Case Studies in the Biomedical Industry." See http://www.mnasq.org/biomedicaldefault.html for details.
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 mailto:Mark@StatEase.com if you have an event coming up with an open slot for a presentation.
7. Workshop alert: Full slate, including DOE for DFSS
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!
--> Experiment Design Made Easy (EDME)
--> Mixture Design for Optimal Formulations (MIX)
--> Response Surface Methods for Process Optimization (RSM)
--> DOE for DFSS: Variation by Design (DDFSS)
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:firstname.lastname@example.org.
I hope you learned something from this issue. Address your general questions and comments to me at: email@example.com.
Mark J. Anderson, PE, CQE
PS. Quote for the month—Inventor of DOE suggests alternative to
one question at a time for prying secrets loose from nature:
PPS. The old-fashioned alternative to DOE is often referred to as
OFAT, or one factor at a time. However, I recently came across
another acronym for this: COST, or changing only a single thing.
Acknowledgements to contributors:
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