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Introduction to Fractional Factorial Designed Experiments

Posted on June 10, 2013  Comments (6)

Scientific inquiry is aided by sensible application of statistical tools. I grew up around the best minds in applied statistics. My father was an eminent applied statistican, and George Box (the person in the video) was often around our house (or we were at his). Together they wrote Statistics for Experimenters (along with Stu Hunter, not related to me) the bible for design of experiments (George holds up the 1st edition in the video).

The video may be a bit confusing without at least a basic idea of factorial designed experiments. These introductory videos, by Stu Hunter, on Using Design of Experiments to Improve Results may help get you up to speed.

[the video has been removed from the internet]

This video looks at using fractional factorials to reduce the number of experiments needed when doing a multifactor experiment. I grew up understanding that the best way to experiment is by varying multiple factors at the same time. You learn much quicker than One Factor At a Time (OFAT), and you learn about interactions (which are mainly lost in OFAT). I am amazed to still hear scientists and engineers talk about OFAT as a sensible method or even as the required method, but I know many do think that way.

To capture the interactions a full factorial requires an ever larger number of experimental runs to be complete. Assessing 4 factors requires 16 runs, 6 would require 64 and 8 would require 256. This can be expensive and time consuming. Obviously one method is to reduce the number of factors to experiment with. That is done (by having those knowledgable about the process include only those factors worth the effort), but if you still have, for example, 8 very important factors using a fractional factorial design can be very helpful.

And as George Box says “What you will often find is that there will be redundant factors… and don’t forget about those redundant factors. Knowing that something doesn’t matter is almost as important as knowing what does.” If you learn a factor isn’t having an affect you may be able to save money. And you can eliminate varying that factor in future experiments.

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Cancer Risks From Our Food

Posted on December 3, 2012  Comments (3)

comic showing the dangers of drawing false conclusion based on statistical significance

Randall Munroe illustrates RA Fisher’s point that you must think to draw reasonable conclusions from data. Click the image to see the full xkcd comic.

Pretty much everything you eat is associated with cancer. Don’t worry about it. by Sarah Kliff

The changes in cancer risk were all over the map: 39 percent found an increased risk, 33 percent found a decreased risk and 23 percent showed no clear evidence either way.
…
The vast majority of those studies, Schoenfeld and Ioannidis found, showed really weak associations between the ingredient at hand and cancer risk. A full 80 percent of the studies had shown statistical relationships that were “weak or nominally significant,” as measured by the study’s P-values. Seventy-five percent of the studies purporting to show a higher cancer risk fell into this category, as did 76 percent of those showing a lower cancer risk.

Sadly the evidence is often not very compelling but creates uncertainly in the public. Poorly communicated results and scientific illiteracy (both from publishers and the public) leads to more confusion than is necessary. Even with well done studies, good communication and a scientifically literate population nutrition and human health conclusion are more often questionable than they are clear.

Related: Researchers Find Switch That Allows Cancer Cells to Spread – Global Cancer Deaths to Double by 2030 – Physical Inactivity Leads to 5.3 Million Early Deaths a Year

Brian Cox – Lecture on Science and Quantum Mechanics

Posted on December 27, 2011  Comments (1)

Brian Cox gave a wonderful lecture at the Royal Institution of Great Britain. This is one more great thing the internet makes possible: have great fun while you learn. Enjoy.

With the help of Jonathan Ross, Simon Pegg, Sarah Millican and James May, Brian shows how diamonds – the hardest material in nature – are made up of nothingness; how things can be in an infinite number of places at once; why everything we see or touch in the universe exists; and how a diamond in the heart of London is in communication with the largest diamond in the cosmos.

Related: Quantum Mechanics Made Relatively Simple Podcasts by Hana Bethe – Brian Cox Particle Physics Webcast – Physicists Observe New Property of Matter

Science and Engineering Lectures Online

Posted on November 1, 2009  Comments (3)

VideoLectures.Net offers free and open access of a high quality video lectures presented by distinguished scholars and scientists at events like conferences, summer schools, workshops and science promotional events. The portal is aimed at promoting science, exchanging ideas and fostering knowledge sharing by providing high quality didactic contents not only to a scientific community but also to a general public.

Enjoy the great lectures they provide. Also see the Curious Cat directory of science and engineering webcast web sites. There are lots of great presentations available now. The last several years has really seen a huge increase in the valuable webcasts available online.

Related: Science Postercasts – Great Physics Webcast Lectures – Google Tech Webcasts #4 – Toyota Engineering Development Process – Marissa Mayer on Innovation at Google – Canada Film Board Provides Open Access

Nobel Laureate Initiates Symposia for Student Scientists

Posted on June 3, 2008  Comments (1)
The video shows a portion of Oliver Smithies’ Nobel acceptance lecture. See the rest of the speech, and more info, on the Nobel Prize site.

As an undergraduate student at Oxford University in the 1940s, Oliver Smithies attended a series of lectures by Linus Pauling, one of the most influential chemists of the 20th century. It was a powerful experience, one that sparked the young scientist’s ambitions and helped launch his own eminent career.

“It was tremendously inspiring,” says Smithies, one of three scientists who shared the Nobel Prize in Medicine in 2007. “People were sitting in the aisles to listen to him.”

Now Smithies, who was a genetics professor at the University of Wisconsin-Madison from 1960-88, is taking it upon himself to expose a new generation of undergraduates to this sort of experience. Using the prize money that came with his Nobel Prize, Smithies is funding symposia at all four universities he has been affiliated with throughout his scientific career: Oxford, the University of Toronto, UW-Madison and the University of North Carolina, where he is currently the Excellence Professor of Pathology and Laboratory Medicine. Each university will receive about $130,000 to get things started.

“He wants the symposium to be a day when we bring the very best in biology to campus to interact with the students,” says geneticist Fred Blattner, who is in charge of organizing the symposium at UW-Madison and who collaborated with Smithies when their careers paths overlapped in Wisconsin.

The first of two speakers at the UW-Madison’s inaugural Oliver Smithies Symposium will be Leroy Hood, director of the Institute for Systems Biology, located in Seattle. Hood is a pioneer of high-throughput technologies and was instrumental in developing the technology used to sequence the human genome. More recently, Hood has focused his efforts on systems biology, the field of science in which researchers create computer models to describe complex biological processes, such as the development of cancer in the body. He is also at the forefront of efforts to use computer models to help doctors tailor drugs and dosages to an individual’s genetic makeup.
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Quantum Mechanics Made Relatively Simple Podcasts

Posted on February 18, 2006  Comments (3)

Three Lectures by Hans Bethe

In 1999, legendary theoretical physicist Hans Bethe delivered three lectures on quantum theory to his neighbors at the Kendal of Ithaca retirement community (near Cornell University).

Intended for an audience of Professor Bethe’s neighbors at Kendal, the lectures hold appeal for experts and non-experts alike. The presentation makes use of limited mathematics while focusing on the personal and historical perspectives of one of the principal architects of quantum theory whose career in physics spans 75 years.