Creativity defeats sensibility for paper helicopter fly-off
Posted by mark in design of experiments on April 9, 2010
Twice a year I teach a day on design of experiments (DOE) at Ohio State University’s Fisher College of Business. The students are top-flight executives seeking six sigma black belt certification. To demonstrate their proficiency for doing DOE, I ask them to break into teams of three or four and, within a two hour period, complete a two-level factorial on paper helicopters.*
It’s always interesting to see how intensely these teams from industry compete to develop the ‘copter that flies longest while landing most accurately. However, this year one group stood out as being less competitive than the others. Therefore, I was very surprised that they handily won our final fly-off. It turns out that one of their factors was dropping the helicopter either wings-up or wings-down – the latter configuration being completely non-intuitive. It turns out that going upside down makes it easier to drop, the flight time suffers only slightly and the flight becomes far more accurate – a premium in my overall scoring.
“The chief enemy of creativity is ‘good’ sense.”
– Pablo Picasso
Ironically, another team who benefited from having an expert in aeronautical engineering and a very impressive work ethic all around – they did more runs by far than anyone else – never thought of flying the ‘copters upside down. In fact, their team leader objected very vigorously that this orientation must not be allowed, it being clearly unfair. Fortunately, other executives in this black-belt class hooted this down.
I thought this provided a good lesson for process and product improvement – never assume that something cannot work when it can be easily tested. That’s the beauty of DOE – it enables one to screen unknown (and summarily dismissed) factors to uncover a vital few that often prove to be the key for beating the competition.
*I also do this experiment for a class on DOE that I teach every Spring at South Dakota School of Mines and Technology. In fact, I am writing this blog from their campus in Rapid City where I’ll be teaching class tonight. For details, pictures and results of prior experiments here and at OSU, see this 2004 Stat-Teaser article on “Playing with Paper Helicopters”.
Misuse of statistics calls into question the credibility of science
Posted by mark in science, Uncategorized on March 28, 2010
The current issue of Science News features an indictment of statistics by writer Tom Siegfried. He pulls no punches with statements like this:
“…a mutant form of math has deflected science’s heart..”
“Science was seduced by statistics…”
“…widespread misuse of statistical methods makes science more like a crapshoot.”
“It’s science’s dirtiest secret: …testing hypotheses by statistical analysis stands on a flimsy foundation.”
“Even when performed correctly, statistical tests are widely misunderstood and frequently misinterpreted. As a result, countless conclusions in the scientific literature are erroneous…”
Draw your own conclusions on whether science fails to face the shortcomings of statistics by reading Siegried’s article Odds Are, It’s Wrong.
My take on all this is that the misleading results boil down to several primary mistakes:
- Confusing correlation with causation
- Extrapolating from the region of experimentation to unstudied areas
- Touting statistically significant results that have no practical importance
- Reporting insignificant results from studies that lack power to see differences that could be very important as a practical matter.
I do not think statistics itself should be blamed. A poor workman blames his tools.
Test and evaluation of the Great Panjandrum – a spectacular failure for weaponry
Posted by mark in history, science, Uncategorized on March 23, 2010
When time becomes available – mainly while I do cardio-exercise on my home elliptical, I’ve been watching a classic 26-episode BBC series on The World at War that my oldest son gave me. It’s extremely compelling – rated 9.7 out of 10 by over two thousand voters at the Internet Movie Database (IMDb).
This morning I watched the chronicle of D-Day. Being that I just returned from the Annual National Test & Evaluation Conference by the National Defense Industry Association (NDIA), it was interesting to see what the boffins of Britain invented to defeat the defenses put up along the Normandy beaches. Perhaps the most amazing device was the Great Panjandrum, a rocket-propelled cart, which according to this write-up for Wikipedia was developed by the Admiralty’s Directorate of Miscellaneous Weapons Development. (One wonders about the “miscellaneous” bit.) The clip I viewed on the spectacular failure of the Great Panjandrum can be seen (along with other incredibly-inept military devices for D-Day) in a video on British Secret Wartime Follies posted in this article by UK’s Daily Mail. Check it out!
PS. The Brits continue to come up with the most audacious inventions, such as this flame-throwing moped developed as a deterrent against derelict drivers competing for motorway lanes.
Evolutionary operation
Posted by mark in design of experiments, Uncategorized on March 7, 2010
Last December, after an outing by the Florida sea, I put out an alert about monster lobsters. This reminded me of an illustration by statistical gurus Box and Draper* of a manufacturing improvement method called evolutionary operation (EVOP), which calls for an ongoing series of two-level factorial designs that illuminate a path to more desirable conditions.
With the aid of Design-Expert® software, I reproduced in color the contour plot in Figure 1.3 from the book on EVOP by Box and Draper (see figure at the right). To illustrate the basic principle of evolution, Box and Draper supposed that a series of mutations induced variation in length of lobster claws as well as the pressure the creatures could apply. The contours display the percentage of lobsters at any given combination of length and pressure who survive long enough to reproduce. Naturally this species then evolves toward the optimum of these two attributes as I’ve shown in the middle graph (black and white contours with lobsters crawling all over them).
In this way, Box and Draper present the two key components of natural selection:
- Variation
- An environment that favors select variants.
The strategy of EVOP mimics this process for improvement, but in a controlled fashion. As illustrated here in the left-most plot, a two-level factorial,** with ranges restricted so as not to upset manufacturing, is run repeatedly – often enough to detect a significant improvement. In this case, three cycles suffices to power up the signal-to-noise ratio. This case illustrates a big manufacturing-yield improvement over the course of an EVOP. However, any number of system attributes can be accounted for via multiple-response optimization tools provided by Design-Expert or the like. This ensures that an EVOP will produce more desirable operating conditions overall for process efficiency and product quality.
It pays to pay attention to nature!
*Box, G. E. P. and N. R. Draper, Evolutionary Operation, Wiley New York, 1969. (Wiley Classics Library, paperback edition, 1998.)
**(We show designs with center points as a check for curvature.)
Beware of bugs bearing backpacks
Posted by mark in science, Uncategorized on March 3, 2010
I am attending a conference sponsored by the National Defense Industry Association (NDIA). They provided all of us participants a copy of the latest issue (March) of their publication National Defense. While wiling away the time listening to some long-winded higher-ups I paged through the magazine and admired the weaponry developed to keep our war-fighters supported to the max. However, on page 17 a very odd picture caught my eye – a cockroach carrying a radiation sensor on its back! A researcher at Texas A&M reports that these bugs are ideal for sweeping potentially contaminated areas, ideally in teams of twenty. They can be operated remotely via devices that stimulate their leg muscles.
There is one problem though: Cockroaches cannot crawl backward. One had better hope that none of the bad guys wear pointy-toed cowboy boots, because they will be ideal for killing the sensor-bearing bugs that become stuck in the corners.
Simplifying the witches brew in Shakespeare’s MacBeth
Posted by mark in Uncategorized on February 14, 2010
Last week I enjoyed an innovative performance of Shakespeare’s MacBeth at the Guthrie Theater in Minneapolis. The director, Joe Dowling, takes some liberties with the original production, such as dropping the warrior MacBeth on stage down a ninja rope and equipping him with a machine gun. However, mostly the gruesome killings that riddle this dark play are accomplished with old-fashioned daggers and swords.
Being a chemical engineer who abhors overly complicated recipes, it bothers me that the three weird sisters in Macbeth put so many ingredients into their witches brew. It would be very hard to scale up their potent product from bench-level kettle to massive manufacturing. By the way, thanks to this heads-up by Nigel Beale I cracked this coven’s confidential code on components; for example, eye of newt, which cannot be easily sourced, is really readily-available mustard seed. Nevertheless, I’ll bet that a good mixture screening experiment, followed-up by an in-depth formulation design, such as this one on a cell-culture medium, would reveal that only a few key ingredients might do the job for enabling clairvoyance or whatever a witch might be up to.
Keep it simple, I say. Or as Shakespeare advises more eloquently, “Brevity is the soul of wit.”
Skepticism versus cynicism about science experiments
Eric Felten’s latest “De Gustibus” column in Wall Street Journal reports New Episodes of Scientists Behaving Badly. It details various scandals, for example the retraction of a landmark publication linking autism to childhood vaccines. This creates a great deal of cynicism such as that expressed by this parent of a kid she helped on a science project:
“The experiments never turned out the way they were supposed to, and so we were always having to fudge the results so that the projects wouldn’t be screwy. I always felt guilty about that dishonesty, but now I feel like we were doing real science.”
Ouch!
Coincidentally, Stat-Ease received an email from someone who goes by the pen-name “The Pyrrhonist.” (I see a trend here: I need to work on a scholarly-sounding moniker.) While researching pyrrhonism, I came across this skeptical quote by a Greek named Carneades who set the stage for his countryman Pyrrho:
“Nothing can be known, not even this.”
That’s tough to get around!
I truly believe that some degree of skepticism is healthy, such as judicious use of the null hypothesis for assessing the outcome of experiments. However, it’s not good for experimenters to abandon all standards by succumbing to an attitude of scornful or jaded negativity, especially a general distrust of the integrity or professed motives of others – the definition of cynicism (according to the Free Dictionary).
So, be skeptical, but not cynical.
Tiny rotifers defeat the Red Queen
This week’s NPR Science Friday presented a fascinating report on rotifers, also known as “wheel animalcules”* due to the way they rotor food into their cylindrical bodies.** Besides being so funny-looking, these critters are unique in being only female — no guys to bother with (a bit of a bummer coming up as we are to Valentine’s Day). According to the Red Queen hypothesis this single gender situation should have put rotifers at an evolutionary disadvantage. However, these animalcules manage to thrive, albeit plagued by parasites. They survive by tolerating dehydration for amazing-long periods while riding the wind to their next home – typically a single drop of water.
Check out this entertaining Science Friday video on rotifers, which features new research by Paul Sherman and Chris Wilson of Cornell University. Warning: Although this production would be rated “G” for gender, it may not be suitable for children due to some horrifying imagery of lethal fungal parasites.
*Detailed in Welcome to the Wonderfully Weird World of Rotifers
**Seen in the brief video Life in a Drop of Water: Rotifer
Getting straight to the point via the word for today
Posted by mark in Basic stats & math on January 25, 2010
Today I learned a new aspect of geometry – the “symmedians” of a triangle. This esoteric term showed up in a review by Wall Street Journal writer Mark Laswell of a book on personal ads.* Here’s the appeal for a companion that caught my eye:
“Apparently the Three Symmedians aren’t a novelty Bosnian folk troupe. Rubbish mathematician (M 37).”
This diagram and detailing by Wolfram Mathworld tells you how to draw symmedians on a triangle and locate the symmedian point, which is the “isogonal conjugate” of the centroid.
It turns out that the centroid is a vital point for mixture design of experiments aimed at optimizing product formulations, as explained in this primer that I co-authored.
So that explains how the symmedian is an interesting ‘counter-point’ for me. However, I wonder if the self-styled “rubbish mathematician” attracted an isogonal conjugate with his play on geometry.
*(“Lonely Hearts, Like Minds The eccentric personal ads of ‘romantically awkward eggheads”)
Apples and oranges comparison of diets?
Posted by mark in science, Uncategorized, Wellness on January 21, 2010
While exercising on my elliptical machine this morning watching ABC’s Good Morning America the show captured my attention with a report that Weight Watchers (“WW”) this week filed a lawsuit against one of its top competitors, Jenny Craig (“JC”). The dispute stems from a claim by JC that their clients lost, on average, over twice as much weight as those on the largest weight loss program. WW alleges that this claim is deceptive due it comparing a study by JC done this year versus one done by WW 10 years ago. According to this news release by Weight Watchers the complaint states that generally accepted standards of biomedical research require Jenny Craig to compare the two current offerings of both companies through a head-to-head randomized clinical trial.
“You can’t compare studies that were done in different locations at different times using different groups of people.”
– Louis Aronne, M.D, New York Presbyterian Hospital weight loss expert and author of Eat This, Not That
Although the judge has put a temporary restraining order against their offending ad, I wouldn’t rule out the JC claim prima facie. After all, as Smartmoney Magazine writer Angie Marek stated in her column on The Skinny on Big, Fat Diet Programs “the science on most of these plans is hardly conclusive, since most of the research has been paid for by the diet companies themselves.” In fact, I predict that this case will keep at least two statisticians fat and sassy as expert witnesses (one on each side of this tug-of-war).