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:
Yesterday the citizens of our United States exhibited their mercurial mood by voting for a transit in their political landscape from the right to the left. Today they can see the planet Mercury transit the sun. This happens only about every decade. For an astronomer's eye view (Kitt Peak, Arizona), see the webcast from 11 am to 4 pm PST by San Francisco's Exploratorium at http://www.exploratorium.edu/transit/. I expect that they will save the record of this astronomical event if you miss Mercury actually in transit this time around.
1. Faq: Why effects plot may change depending on chosen model
1. FAQ: Why effects plot may change depending on chosen model
You will find the Recalculate button at the bottom of the floating Effects Tool. I advise that you press this button whenever you choose effects. It may make no difference. However, in a non-orthogonal design the size of the effects are dependent upon which others you choose first. Based on your chosen model, the button causes Design-Expert to recalculate the effects and synchronize them with the analysis of variance, which you create by clicking the next button in the sequence of analysis: "ANOVA."
If you then go back to the half-normal (or Pareto) plot and pick more effects, some of those chosen previously may fall back into the pack of trivial many, near zero. I realize that this analogy is a stretch, but this changing situation reminds me of my childhood days when we would get a group of boys together for a game, choose two captains and let them pick players. Sometimes a really good player would saunter in after sides were chosen, and then one hapless boy would be kicked off a team to make room for the star. In other words, the individual term that stood out initially, falls back into the pack after one that is better steps forward.
"Thanks for your quick answers. A good technical support is one of the decisive things that I look for when choosing software."
(Learn more about factorial model-building by attending the three-day computer-intensive workshop "Experiment Design Made Easy." See http://www.statease.com/clas_edme.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.)
*See http://www.statease.com/soft_abs.html for details and link from there to free 45-day fully-functional trials of version 7 of Design-Expert software.
2. Info alert: Poking fun poetically at DOE and statisticians
Our UK associate Alan Collins (see him pictured and introduced at http://www.statease.com/acollins.html) dredged up an old, but still good as gold, poem on DOE titled "Hiawatha Designs an Experiment."* It is a bit too long to re-print here, but you can read it at http://www.math.utah.edu/~cherk/hiawatha.html. If you are in a mood for geeky humor collected by Andrej and Elena Cherkaev, mathematics professors at the University of Utah, click the "back to math jokes" link at the end of this devilishly funny poem on DOE.
*Attributed to various authors in numerous reprints on the internet, but so far as I can tell, it was written by British statistician Maurice Kendall who in his prime produced double the number of random digits, over one hundred thousand, than ever before. Before doing this, he developed a four-test gauntlet that defined whether a series of numbers really are random. For more on Maurice, see http://en.wikipedia.org/wiki/Maurice_Kendall.
PS. Here's a shorter poem I found on the internet:
THE MAGIC OF STATISTICS
The statistician spends his days,
3. Event alert: Do you seek a speaker?
Do you need a speaker on DOE for a learning session within your company or technical society at regional or national levels? If so, contact me. It may not cost you anything if Stat-Ease has a consultant close by. 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 — we are at the foremost ranks of practical expertise on design of experiments for process and product improvement. Contact me at Mark@StatEase.com if you have an event coming up with an open slot for a presentation.
PC. Click http://www.statease.com/events.html for a list of appearances by Stat-Ease professionals. We hope to see you sometime in the near future!
4. Work alert: Last chance for "Experiment Design Made Easy"
The last public presentation of "Experiment Design Made Easy" for 2006 will be held on December 5-7 at the Stat-Ease computer training center in Minneapolis. See http://www.statease.com/clas_edme.html for further information and link from there to register online. See http://www.statease.com/clas_pub.html for 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 Stat-Ease at 612.378.9449. 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.* Call us to get a quote.
*Believe it or not, it only takes a class of 4 students to make it economical for Stat-Ease to come and teach at your site versus sending them out to one of our public presentations. The economics are detailed in the July 2006 issue of the Stat-Teaser newsletter at http://www.statease.com/news/news0608.pdf.
I hope you learned something from this issue. Address your general questions and comments to me at: Mark@StatEase.com.
Mark J. Anderson, PE, CQE
PS. Quote for the month — A compelling call for scientists and engineers to learn statistics:
Acknowledgements to contributors:
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