Stats Made Easy

Practical Tools for Effective Experimentation

Monday, September 25, 2006

Longer-term perspective on global warming (and other catastrophes)

On March 16th I blogged about the sharp upturn in global temperatures that some liken to the blade of a hockey stick. The blog provides a link to a graph reproduced by the BBC which goes back 1000 years. Aside from questions about how data are fitted, simple changes to scales and other attributes of the graphs themselves can paint very different perspectives on seemingly straightforward scientific questions such as whether we ought to be worried about global warming. Andy Sleeper shows this in part 7 of his white paper titled HOW TO LIE WITH STATISTICAL GRAPHICS. The color-coded graph generated by the U.S. National Oceanographic and Atmospheric Administration is very alarming. However, it only provides 122 years of history and the y-axis scale is restricted to about 2 degrees C. A few figures later in Sleeper's paper one sees another graph based on 400,000 years of temperatures estimated from core samples of Antarctic ice. It reveals cyclic temperature swings of 12 degrees C! In this context, should a less than 1 degree increase in global temperature be considered abnormal, that is, due to a special cause such as man-made carbon dioxide?

PS. Here's something to really worry about. The November issue of Sky and Telescope features a heads-up on "The Most Dangerous Asteroid Ever Found" -- a 1000-foot pile of rock called Apophis. It will just miss the Earth on April 13, 2029. If Apophis hits a narrow zone -- called the keyhole, it will be dragged enough by our gravity to put it on a course that collides with Earth seven years later. One can only hope that NASA's proposed gravity tractor will pull the asteroid off target and save the planet.

Friday, September 22, 2006

Experimental proof that microwaved water kills plants?

A fellow graduate from University of Minnesota's chemical engineering school told me this week that "I am afraid the average person’s level scientific understanding in this country is in the dark ages." His skeptical comment, with which I am sorry to say I agree, stemmed from an inflammatory email passed along to both of us by a mutual friend, an attorney who has been deemed a "super-lawyer" by his peers. No offense, but I do not think his expertise extends to the scientific arena. (Similarly, I make no claim to knowledge of law.) The email he circulated from internet comes with this cover comment "An engineer friend of mine sent this and added that it 'Seems to be legitimate!' Wow!" Attached are photographs from a simple comparative experiment that apparently supports the commentator's contention that "microwaved anything...corrupts the DNA in the food so the body can not recognize it." It concludes by saying: "Proof is in the pictures of living plants dying. Remember You are also Living. Take Care." See the photos and commentary for yourself at -- a site maintained by Barbara and David Mikkelson that follow up on "urban legend." Their articles seem to be well-researched, intelligent, and full of common sense. Why do average people, or in this case -- clearly someone far above the mean for general intelligence, seem to be so gullible about legends like this one about the dangers of microwaves? David Mikkelson provides this explanation: "The power of illustrative anecdotes often lies not in how well they present reality, but in how well they reflect the core beliefs of their audience."

Sunday, September 17, 2006

Surveys produce precisely inaccurate findings

In New Brighton, Minnesota, my old home town, the city council paid $4,600 for a a survey that asked how many residents voted in the last election. It found that 47 percent of the 400 respondents said they "always" vote when, in fact, less that 18 percent showed up for the last election. Professor Sandford Weisberg, director of the University of Minnesota's Statistical Consulting Service, wasn't surprised by this. He says that "people always want to say what pleases people." However, the pollster hired by New Brighton claims that the people he surveyed simply "misremembered" that they hadn't voted. A recent article in New York Times opinion pages* provides much more alarming evidence of misleading surveys, for example, one by American Medical Association (AMA) that reported an alarming rate of binge drinking and unprotected sex among college women during spring break. The AMA survey, supposedly based on a random sample of 644 women, provided a margin of error of +/– 4 percent. However, according to the Times, the survey included only women who volunteered to answer questions — and only a quarter of them had actually ever taken a spring break trip! The article goes on to cite other cases of surveys that produced very misleading results, including one similar to the one done by New Brighton. Beware of what you read about what other people think, especially if it comes from a scientific survey.

*Precisely False vs. Approximately Right: A Reader’s Guide to Polls, by Jack Rosenthal, August 27, 2006

Tuesday, September 12, 2006

Stat-Ease credited with reporting the world's largest flying disk

Our periodic search of internet netted a Google group exchange on "...the biggest Frisbee made"* in which someone named "Burp" (whose email starts with "Beerme"!) provides the link to this incredible photo. It was sent to me in 2002 by Darrell W. Pepper, Ph.D., Dean, College of Engineering, University of Nevada Las Vegas, who said "I enjoyed your article in the September issue of the Stat-Teaser regarding the flying rings/disks with your daughter (Sixth-Graders Experiment with Flying Disks). I just thought you might like to know that we built the world's largest flying disk (10 ft in diameter) some years ago - as well as a 10 ft ring (using mylar and PVC pipe). I also had a grad student do his MS thesis on frisbee/disk aerodynamics a few years back. See the attached picture of one of our former engineering students (who also played center for the UNLV football team) actually throwing the disk (Adler design - like Aerobie but solid). The disk was made from composite material and foam - total weight was about 20 lbs. The student tossed the disk about 75 feet. By the way, when we transported it to Reno for the annual AIAA meeting (about 400 mi), a wind came up and blew it off the trailer - the student walked over 1000 feet in the desert to pick it up (an unofficial distance record?) The following year I had some students work on a giant machine to toss the disk. It never materialized, but the idea seemed good. We then went on to build solar airplanes, etc. One more thing - there was a report of a UFO disk-shaped object flying over the highway."

PS. Other readers of my original article on the experiment by my daughter weighed in on the effect of color on the plastic disks' physical properties, the impact of a learning curve for throwing them, and the throwers' level of expertise -- see item #2 at my October 2002 DOE FAQ Alert. (Feel free to subscribe at DOE FAQ Alert signup.)

*If you are a fan of flying disks and do not mind some playground language, take a look at the topic in

Monday, September 04, 2006

Pinning down the possibility of scents enhancing athletic prowess

"Welcome to the nebulous world of aromatherapy, where, for a small price, you can, say its proponents, sniff yourself to a sharper mental state, which could lead to more productive workouts. But be wary, for this can be a realm populated by hobbits, trolls and fairy godmothers--more fiction than fact." -- Frank Claps, Training Scents, Men's Fitness, May, 2002.

Recent research by Alan Hirsch of The Smell & Taste Treatment and Research Foundation in Chicago found that bowlers who wore surgical masks impregnated with the aroma of jasmine knocked down 27 percent more pins than those who went scent free*! In a special to the Stamford Advocate picked up by my local newspaper, humorist Jerry Zezima, interviewed Hirsch, who speculated that jasmine counteracts the negative smells in bowling alleys -- smoke, sweaty socks, stale beer, spicy pizza and the like. Zezima's attempts to try reproducing this dubious aromatherapeutic effect provide a great lesson in how not to do an experiment. Here are the results:

-- Game #1, a "few pins" more with jasmine mask (alternated frame-by-frame with scentless) -- final score: 124.

-- Game #2, "much better" with beer sprinkled on scentless mask (vs jasmine) -- final score: 93.

I suppose one could say that Zezima's results go back to frame number 1, that is, they provide no confirmation of Hirsch's findings favoring jasmine. The reason all this caught my eye is that I am the author of tutorial on setting up a simple comparative bowling experiment: Design-Expert 7 Software General One-Factor Tutorial. However, I have no interest in applying better design of experiments (DOE) to this questionable effect of scents. The mask would get in the way of drinking my beers and talking with my bowling buddies. That's what's really important! Who cares about the score?

PS. Obviously I am not a very 'scents'itive fellow, so jasmine would be wasted on me. The sweaty socks are tolerable, but I do believe that eliminating smoking would definitely enhance the athletics and general healthiness of outings to the neighborhood alley.

*EFFECTS OF AROMA ON AMATEUR TEN-PIN BOWLING PERFORMANCE presented to Association for Chemoreception Sciences on April 30, 2006