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.
This plain text message may be easier to read if you do not remove the line breaks. If you use Microsoft Outlook, press the bar labeled "Extra line breaks in this message were removed." In newer versions select "Restore line breaks."
Here's an appetizer to get this Alert off to a good start: See our
new blog http://statsmadeeasy.net
for lots of fun chat with a statistical/scientific/engineering bent.
My profession of chemical engineers often refer to ourselves as 'comical
en-grin-eers,' so be forewarned that the submissions to Stats Made
Easy blog from me may be somewhat frivolous. Contributions from other
statisticians at Stat-Ease, while less frequent, will likely be far
more weighty. Feel free to comment on Stats Made Easy blogs. You may
do this without entering your e-mail address. However, all entries
are subject to my moderation of content considered abusive, illegal,
defamatory, libelous, indecent, obscene, offensive, or threatening
in any way. Many of you may make use of RSS (Really Simple Syndication)
readers, which track and aggregate updates from your favorite web
sites. As a user of Microsoft Outlook, I recommend RSS Popper freeware,
which loads up quickly, is very intuitive to use and not too intrusive.
You can download it from http://rsspopper.net/2004/10/home.html.
Then right-click on Stats Made Easy link to "Site Feed"
and choose "Subscribe in RSS Popper" to be notified of new
blogs from me or our statistical consultants at Stat-Ease. FYI, here
are the select few blogs that divert my attention:
1. FAQ: Why a p-value is not provided for variance from blocks
PS. Quote for the month: Hunting for effects of practical importance
that are statistically significant.
1. FAQ: Why a p-value is not provided for variance from blocks
To add to what Shari says, I found this quote from the section
on randomized complete block designs in the Second Edition of "Design
of Experiments: Statistical Principles of Research Design and Analysis"
by Robert O. Kuehl, Professor Emeritus at the University of Arizona (http://ag.arizona.edu/arec/dept/faculty/kuehl.html):
"There is little interest in formal inferences about block
effects, and the F statistic is generally not computed for this
purpose even though it may appear in the output of a computer program."
(Learn more about blocking by attending the three-day computer-intensive
workshop "Experiment Design Made Easy." See http://www.statease.com/clas_edme.html
for a course description. Link from this page to the course outline
and schedule. Then, if you like, enroll online.)
2. Info alert: Review of DOE software favors Design-Expert
From: Quality Assurance Engineer in Wichita, Kansas "I am trying hard to buy Design-Expert version 7 (DX7) software, but I need some information from you guys. I began using DX software in 2003 and although I am convinced by any means to buy it for myself, I am having a hard time trying to convince my company that they should purchase corporate licenses. Please send me any information that will tell me how Design-Expert would be better for doing DOE than Minitab and other general statistics packages, as well as ones like yours that are dedicated to DOE."
I like the bit where the author, Felix Grant, says that "Stat-Ease is known for the jokily accessible examples—a tradition continued in DX7's documentation with, for example, an experiment to discover whether Stat-Ease principal Mark Anderson can sleep longer in the morning without being late for work." :)
It's good to have some fun (in my opinion), but on a more serious note, Felix provides this telling observation on how Stat-Ease dedicates itself to providing the best program on the globe for design and analysis of experiments, which becomes possible only by not letting ourselves get sidetracked trying to supply all statistical tools for everyone: "DX7 would never be a replacement for a generic package. Nor does it try to 'function creep' into the territory of such a package. On the other hand, I've frequently encountered cases of a heavyweight analytic package being used to monitor simple descriptive measures for input and output values from a DoE system—and that is definitely using a shotgun to hunt crayfish."
Finally, the bottom line from this Scientific Computing World
reviewer of DOE software is that he puts it to good use for
his own consultancy: "All the projects into which I took
DX7 over the past three months
(For details on DX7 software, including "What's New—The Highlights," see http://www.statease.com/pubs/dx7brochure.pdf.
Download a free, fully-functional 45-day trial of Design-Expert
V7 at http://www.statease.com/dx7trial.html.
Pricing for new licenses and upgrades can be seen at the Stat-Ease
e-commerce site: http://www.statease.com/prodsoft.html.)
3. Reader response: Getting the edge on Occam's Razor
Last month's DOE FAQ Alert* featured comments by Stat-Ease Consultant Wayne Adams on Albert Einstein's quote "Everything should be made as simple as possible, but not one bit simpler." Wayne's mention of Occam's Razor generated this exchange with Tom Scripps, a contract trainer for Stat-Ease (see Tom pictured at http://www.statease.com/tomscrip.html). Tom asked, "WayneI am stumped for the momentdo you know why it's a razor?" Wayne answered, "Razor is a late English corruption of the Middle English 'rasor' which, used as a verb, is to cut off the non-essential. It has to do with razing your assumptions until bare explanation is left."
Coincidentally, Wayne sent me this heads-up: "I've been running some trials (not very scientific I'll admit) of my old razor [Gillette Sensor (two blades)] against the new Fusion Power (five blade, plus a sixth for 'close' work) that I bought last week. In terms of time to shave, closeness of the shave, nicks acquired during shaving, and number of shaves before performance declines, so far the Fusion is a cut above." Not only has Gillette gone crazy with this razor but also with their hyperbolic web site (warning: do not click this link unless you have a very fast internet connection and some time to kill!): http://www.gillettefusion.com/us/. Oh, and by the way, I bought the five-bladed Fusion and, like Wayne, feel that it works better than my old two-bladed razorso much for the saying "the simpler, the better"!
*Back issues viewable below.
4. Events alert: First European DOE User Meeting
The "First European DOE User Meeting" for Design-Expert and Design-Ease Users" will be held at the Faculty Club in Leaven, Belgium on April 24 and 25. This DOE conference is sponsored by Stat-Ease with hosting by CQ Consultancy and participation from other European resellers of Design-Expert and Design-Ease software. See details at http://www.cq.be/DOEconference/. The meeting is a must for European users of Stat-Ease software and perhaps the perfect excuse for those elsewhere to take in the sights in Leuven and surroundings. I lunched at the city center some years agoit was very beautiful!
for a complete list of appearances by Stat-Ease professionals. We
hope to see you sometime in the near future!
5. Workshop alert: Crash Course on DOE for Sales & Marketing
(If you are a corporate technical professional, please pass this news on to your business people!) Quickly identify those factors which affect your sales and marketing results. Learn how they interact and apply that knowledge to make breakthrough increases in sales and profits. Attend the newly expanded two-day Crash Course on DOE for Sales & Marketing at the Stat-Ease training center in Minneapolis on April 19-20. See the course description and links to the syllabus and online enrollment at http://www.statease.com/clas_smdoe.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 1.612.378.9449. 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.
I hope you learned something from this issue. Address your general questions and comments to me at: Mark@StatEase.com.
PLEASE DO NOT SEND ME REQUESTS TO SUBSCRIBE OR UNSUBSCRIBE—FOLLOW THE INSTRUCTIONS AT THE END OF THIS MESSAGE.
Mark J. Anderson, PE, CQE
PS. Quote for the
monthHunting for effects of practical importance that
are statistically significant:
"The effects plot flushes
the birds and the stats shoot them down."
This is a work in progress that came up as an
ad lib during a teleconference on analysis of two-level factorials
for ruggedness testing*in particular the value of producing
a half-normal plot of effects. Here's a thread of conversation I had
with Peter afterwards. I said,"Peter, so far as I am concerned,
you scored a direct hit by saying this. Is this something you made
up on the spot, or did you hear it from someone else?" He said,
"Actually, I just made it up on the spotthe recent story
about our vice president crossed my mind at the moment. I think what
I said or meant to say is 'the effects plot flushes the birds and
the statistical test shoots at them.' The alternative wording is suggested
because "shoot them down" has the implication that you succeed.
A detail that is key to me is that when you shoot, it's a matter of
chance whether you get a hit or miss (or bag your hunting companion!
Now that you point it out, it really is a pretty good metaphor. If
you hadn't captured it, I'd have forgotten, so this is more yours
than mine." Do you readers have any suggestions for refining
Peter's hunting metaphor?
PS. Wayne Adams adds this comment: "The half-normal plot always makes sure the birds flush out front, so you are less likely to pick-off the wrong target!"
*(See December Stat-Teaser cover-page article "Struggle for
Power vs. Resolution vs. Simplicity in an ASTM Standard" at http://www.statease.com/news/news0512.pdf.)
Trademarks: Design-Ease, Design-Expert and Stat-Ease are registered trademarks of Stat-Ease, Inc.
Acknowledgements to contributors:
in previous FAQ DOE Alert e-mail newsletters?
Click here to add your name to the DOE
FAQ Alert newsletter list server.
2021 E. Hennepin Avenue, Ste 480
Minneapolis, MN 55413-2726
p: 612.378.9449, f: 612.378.2152