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Vol: 11 | No: 6 | Nov/Dec'11
Stat-Ease
The DOE FAQ Alert
     
 

Heads-up (below!)
Timeless advice by George Box on getting the gist of multifactor testing

Warning:
Due to issues with our List Server, your subscription may be interrupted.  If you do not see the January-February issue by March 1, 2012, pull this DOE FAQ Alert back on screen and click here to re-subscribe. You will find this link by going to our home page (www.statease.com), choosing Publications from the top links, going to the one for DOE FAQ Alert and scrolling down to where it says “Click here to add your name to the DOE FAQ Alert newsletter list server.”

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 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 this registration page.

Also, Stat-Ease offers an interactive website—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: Analysis, Topic: “Analysis of my case...”, Question: “…coded factor and uncoded factor... when to use them???”

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. Recent threads feature comments on:

  • When can I run my DOE?
  • A DOE study on a wet-massing high-shear granulation
  • Do I really need to randomize?
  • The Top 3 reasons DOEs Fail
 
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Topics discussed since the last issue of the DOE FAQ Alert (latest one first):

Also see the new comments on older posts. 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: stathelp@statease.com.


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Topics in the body text of this DOE FAQ Alert are headlined below (the expert ones, if any, delve into statistical details):

1:  News alert: Stat-Ease Consultants win Shewell Award for the best talk at the 2010 Fall Technical Conference—“Practical Aspects of Algorithmic Design of Physical Experiments”
2:  FAQ: How do I re-compute power for a factorial design?
3:  FAQ: Why do predicted versus actual plots vary from one display to the next?
4:  Reader response: “Design-Expert Diagnostics Saves Experiment (and Postgrad Student)”
5:  Info alert: Peer-reviewed case study on a pharma process development using DOE
6:  Webinar alert: Basics of Response Surface Methodology (RSM) for Process Optimization, Part 2
7:  Events alert: Where and when to hear from Stat-Ease and see their latest tools
8:  Workshop alert: See when and where to learn about DOE
 
 
PS. Quote for the month: Sage words from DOE guru George Box.
(Page down to the end of this e-zine to enjoy the actual quote.)


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1: News alert: Stat-Ease Consultants win Shewell Award for the best talk at the 2010 Fall Technical Conference—“Practical Aspects of Algorithmic Design of Physical Experiments”

Congratulations to Stat-Ease Consultant Pat Whitcomb and his co-author Wayne Adams for being this year’s winners of the Shewell Award for the best presentation at the 2010 Fall Technical Conference, co-sponsored by the ASQ Statistics Division, jointly with the ASQ Chemical and Process Industries Division and two sections of the American Statistical Association: the Section on Physical and Engineering Sciences and the Section on Quality and Productivity.  Pat’s presentation on “Practical Aspects of Algorithmic Design of Physical Experiments” scored highest among many excellent talks on statistical tools.  He accepted the award at this year’s FTC.  This is the third time that Pat has co-authored a Shewell-awarded talk.  See an updated version of his presentation on “Practical Aspects of Algorithmic Design of Physical Experiments” here.


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2: FAQ: How do I re-compute power for a factorial design?

Original Question:

From a Senior Chemist:
“I'm evaluating a factorial model for power. I want to go back and edit my standard deviation and difference levels to observe the effect on power.  How can I do that?”

Answer:

From Stat-Ease Consultant Wayne Adams:
“If you are just modifying the signal-to-noise ratio, the easiest place to do that is under the Evaluation node.  Click the Options button to access three fields where you can enter new ratios for evaluation (the default values are 0.5, 1, and 2).

Evaluation Options
Evaluation Options

OK your new entries.  Then, while still on the Model screen, change the Order to Main Effects.

Evaluating Main Effects Model
Evaluating the Main-Effects Model

Finally, press the Results button and scroll down the report to find the re-calculated power estimates (or simply press the Terms (Power) on the floating bookmark tool).”

(Learn more about power 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: FAQ: Why do predicted versus actual plots vary from one display to the next?

Original Question:

From a Rocket Scientist:
“I recently downloaded Design-Expert version 8 for evaluation.  While testing it I ran across a case where the predicted vs. actual plot in the Diagnostics tab was different than the Model Graphics case.  Sometimes I would get the same plots in both tabs and other times they were different. Could you please explain this behavior?”

Answer:

From Stat-Ease Consultant Brooks Henderson:
“This is working the way it's supposed to—given you included center points in your design.  Notice in the ANOVA (analysis of variance) report how the software presents two models.  The first is the unadjusted model, which uses all the data—including center points.  The second model is adjusted by an aliased curvature term—essentially removing the influence of center points.  By comparing these two models you can see if any lack of fit stems from the center points (curvature) and/or at the factorial points.  For more details, read the annotation on the ANOVA page (turn this on via the View menu).

By default, the adjusted model is used for diagnostics and the unadjusted model is used for the model graphs, hence the disagreement.  Select the View for unadjusted model to make the diagnostics graph match what is presented in the model graphs.”

Changing View from Default Diagnostic View, Adjusted, to Unadjusted Model
Changing the View from the Default Diagnostic View, Adjusted, to an Unadjusted Model

(Learn more about dealing with curvature by attending the two-day computer-intensive workshop Response Surface Methods for Process Optimization.  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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4: Reader response: “Design-Expert Diagnostics Saves Experiment (and Postgrad Student)”

Statistician Paul Mullenix details how “Design-Expert Diagnostics Saves Experiment (and Postgrad Student)” here.  He concludes by saying that “the versatile features within Design-Expert for checking design properties including diagnostics allowed this student to achieve a valid analysis, and, oh yes, graduate on time with no tears.”  We like that!


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5: Info alert: Peer-reviewed case study on a pharma process development using DOE

Matthew N. Bahr, an investigator at GlaxoSmithKline in Collegeville, PA, detailed A Design of Experiments for Tablet Compression for the October issue of PHARMACEUTICAL TECHNOLOGY (Volume 35, Issue 9).  In this peer-reviewed case study on process development Bahr put Design-Expert software to good use for improving the manufacture of tablets.  He started with a two-level factorial design that then was augmented to a central composite design for response surface method (RSM) optimization.


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6: Webinar alert: Basics of Response Surface Methodology (RSM) for Process Optimization, Part 2
Response Surface Methods (RSM) can lead you to the peak of process performance.  In this intermediate-level webinar presented on Tuesday, January 24 at 2:00 PM CT,* Stat-Ease Consultant Brooks Henderson will present a second round of education on response surface methods (RSM) for optimizing processes.

If you are new to RSM, this webinar is for you!  If you missed part 1, do not worry—we posted the recorded presentation by Consultant Shari Kraber here.

Stat-Ease webinars vary somewhat in length depending on the presenter and the particular session—mainly due to breaks for questions: Plan for 45 minutes to 1.5 hours, with 1 hour being the target median.  When developing these one-hour educational sessions, our presenters often draw valuable material from Stat-Ease DOE workshops.

Attendance may be limited, so sign up soon by contacting our Communications Specialist, Karen Dulski, via karen@statease.com.  If you can be accommodated, she will provide immediate confirmation and, in timely fashion, the link with instructions from our web-conferencing vendor GotoWebinar. *(To determine the time in your zone of the world, try using this link.  We are based in Minneapolis, which appears on the city list that you must manipulate to calculate the time correctly.  Evidently, correlating the clock on international communications is even more complicated than statistics!  Good luck!)


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7: Events alert: Where and when to hear from Stat-Ease and see their latest tools

Click here 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 reimbursement for travel expenses.  In any case, it never hurts to ask Stat-Ease for a speaker on this topic.


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8: 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 SDOE and DELS in February to earn $295 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 workshops@statease.com.


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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@statease.com.

Sincerely,

Mark

Mark J. Anderson, PE, CQE
Principal, Stat-Ease, Inc.
2021 East Hennepin Avenue, Suite 480
Minneapolis, Minnesota 55413 USA


PS. Quote for the month—sage words from DOE guru George Box:


"
If we could begin by just getting engineers to run a few simple designs, this will usually whet their appetite for more. For there are hundreds of thousands of engineers in this country, and even if the 2^3 was the only design they ever used, and even if the only method of analysis that was employed was to eyeball the data, this alone could have an enormous impact on the experimental efficiency, the rate of innovation, and the competitive position of this country.


—George Box


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, 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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DOE FAQ Alert ©2011 Stat-Ease, Inc.
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