Too many dogs at farmers markets?
Today’s “Gray Matter” column in the New York Times provides an exceptionally well-balanced report that casts doubt on the healthiness of food from farmers markets—read it here. What caught my eye is how the author, a professor at University of Minnesota (my alma mater), lays out a number of positive correlations (being careful not to conclude causation) between farmers markets and various food-borne illnesses, including one attributed to the ‘droppings’ from dogs and the like. But the thing I most admire is him admitting to “a number of dogs that did not bark”, i.e., a number of outbreaks that did not show a statistically significant connection to farmers markets.
This suggestion of possible health issues with farmers markets is heavily hedged—very possibly it will not be borne out by subsequent research. Nevertheless it would only be prudent to thoroughly wash locally grown and sold produce.
Sine illusion makes peaks and valleys on graphs look overly variable
An article in the latest Journal of Computational and Graphical Statistics (JCGS, Vol 24, Num 4, Dec 2015, p1170)) alerted me to a fascinating misperception called the “sine illusion” that causes misinterpretation of trends in variability. See it nicely illustrated here by vision researcher Micheal Bach. The JGCS, Susan VanderPlas and Heike Hofmann, detail “Signs of Sine Illusion—Why We Need to Care” and provide methods to counteract its misleading effects.
If you see a scatter plot that goes up and down with seemingly large scatter at the bends, get out a ruler to get the true perspective. That is my take home message for those like me who like to be accurate in their assessments of data.
“The illusion is explained in terms of a perceptual compromise between the vertical extent and the greater overall dimensions of the section at the turn of the sine-wave figure.”
– RH Day and EJ Stecher, “Sine of an illusion,” Perception, 20; 1991, 49–55.
A knotty problem—how to keep track of stuff without computers or even pen and paper
Posted by mark in history, Uncategorized on January 3, 2016
The New York Times reports today on the recent discovery of several knotted string records, called khipus, that ancient Incas used to record things such as the colorful potatoes I photographed at a Peruvian market. From what I saw on my travels there—see this blog on Incan agriculture experiments, a great deal of food must have been produced and stored.
Based on this Times picture I suspect these “mops that have seen better days”, as George Gheverghese Joseph, a mathematics historian at the University of Manchester, U.K., put it, must be a bit easier to untangle than Christmas lights. But then there remains the problem of deciphering them.
Thus far researchers have picked up on mathematical aspects of the khipus. However, the latest trove of colored strings provides a chance at figuring out the Incan scheme for identifying what was being counted. Here is where database capability and statistical methodology comes in handy.
I amazes me how all of the technology we now have at our disposable is challenged by methods developed 600 or so years ago. Hats off to Incan ‘thinken!
“Many now think that although khipu probably began as accounting tools, they had evolved into a writing system—a kind of three-dimensional binary code, unlike any other on Earth—by the time the Spanish arrived.”
— Cracking the Khipu Code Science magazine.
College textbooks up over 1000 percent since ’77
Bernie Sanders say it’s time to make college tuition free. That would really be radical. A more attainable goal is to make textbooks more affordable. According to an NBC story posted just prior to the current school year, college textbook prices have risen 1,041 percent since 1977, now amounting to over $1200 per student per year. My high school classmate Mark Perry, Professor of Economics at University of Michigan, warns that:
“College textbook prices are increasing way more than parents’ ability to pay for them.”
This tide of expenses for books has been slowed somewhat by the advent of rentals, e.g., $34 for one semester versus $157 to buy Montgomery’s 8th Edition of Design and Analysis of Experiments.
Another way to save that no one dreamed of in ’77 is by buying an e-textbook—Montgomery’s DAOE book costing only $67 in this format.
However, the big breakthrough in reducing the cost of college comes from the University of Minnesota’s Open Textbook Network (OTN), which began offering textbooks for free three years ago. Students over this period saved an estimated 1.5 million dollars, primarily over the past year.*
Professor Gary Oehlert of U Mn School of Statistics—a long-time advisor to Stat-Ease and author of A First Course in Design and Analysis of Experiments**—provides this endorsement of this worthy initiative by my alma mater: “There are several other similar open textbook depositories (OpenStax, etc), but OTN was one of the first to have reviews for the books as well as perhaps being the only one to have a support model for obtaining serious reviews of the books. It also has a broader range of texts than one might anticipate, with math books ranging from high school level through some fairly advanced topics.”
Powerful forces from for-profit publishers and authors who prefer being paid for their hard labor will naturally restrict the spread of free books. Even so, the OTN will certainly put a damper on the rampant inflation of the cost of texts. That will be a big relief for hard-pressed students and their parents.
*Source: “One for the Books”, Minnesota Alumni magazine, Winter 2016, p.12.
**Freely available here under Creative Commons license
Merry DXmas!
Design-Expert software produced this graphic with some wizardry by our Consultant Wayne Adams. Amazing!
Happy holidays!
Technology advanced beyond any hope for healthy curiosity
I am watching the Syfy’s series “Childhood’s End” this week. It is based on a science fiction novel by British author Arthur C. Clarke, one of my favorites growing up. One of the main characters is a very bright boy who at the end of the premier episode last night becomes an astrophysicist, despite this scientific profession being made entirely superfluous by the advanced technology of the alien Overlords.
This morning Robert Scherrer, the chairman of the department of physics and astronomy at Vanderbilt University, lamented in an editorial* for Wall Street Journal that children no longer have any reason to be interested in science, mainly because most of our household gadgets fall into the category of magic—alluding to Clarke’s observation that “any sufficiently advanced technology is indistinguishable from magic.”
“The world’s now placid, featureless, and culturally dead: nothing really new has been created since the Overlords came. The reason’s obvious. There’s nothing left to struggle for, and there are too many distractions and entertainments.”
― Arthur C. Clarke, Childhood’s End
Sleep well or get fat
Posted by mark in Uncategorized, Wellness on November 10, 2015
It’s not often I see a study that focuses on variability but that is what drives this recent New York Times story detailing how “Poor Sleep May Spur College Weight Gain.” Sleep for Science Lab researchers kept track of how 132 first-year students at Brown University slept over a nine week period, during which more than half of them gained nearly six pounds. The increase in weight comes as no surprise (one subject gained 18 pounds!) but this correlating to deviations in sleeping times is provocative. Whether this is causal, or just an offshoot of other upsets in lifestyle that come when students break loose from their parents, remains to be seen in controlled experiment.
Meanwhile, the National Sleep Foundation (NSF) widened ranges earlier this year (2/2/15) in these new recommendations in hours per day broken down by age:
- Newborns (0-3 months): 14-17 (previously 12-18)
- Infants (4-11 months): 12-15 hours (14-15)
- Toddlers (1-2 years): 11-14 hours (12-14)
- Preschoolers (3-5): 10-13 hours (11-13)
- School age children (6-13): 9-11 hours (10-11)
- Teenagers (14-17): 8-10 hours (8.5-9.5)
- Younger adults (18-25): 7-9 hours (new age category)
- Adults (26-64): 7-9 hours (no change)
- Older adults (65+): 7-8 hours (new age category)
My interpretation of all this is to get your teens to follow a fairly regular schedule for sleep (good for those of all ages, I feel sure), but don’t worry too much about the exact amount, provided it falls within the recommended guidelines of NSF.
P.S. In this report published November 4 in Sleep Review, Russell Foster, professor of circadian neuroscience at Oxford, recommends you brush your teeth in the dark to ensure a good sleep. That gives me a bright idea: glow in the dark toothpaste! 🙂
Breaking free of standard practices that no longer make sense
Posted by mark in Consumer behavior, Uncategorized on October 20, 2015
Building off my previous blog on “Why no one wants to monkey around with how things have always been done” I am passing along an insightful anecdote by David Morganstein, President of the American Statistical Association, about his wife’s standard practice to slice a quarter inch off of every ham and toss it in the trash. Read this amazing story and others like it in “The Slice of Ham, How Do You Know?”.
Most of our assumptions have outlived their uselessness.
– Marshall McLuhan, famed for predicting the World Wide Web almost thirty years before it was invented.
Are you a super-recognizer?
Every now and then I see someone in an airport or other public place who looks very familiar. Now and then I’ve actually walked up to someone and greeted them by name and gotten a blank, off-putting look in return. That is embarrassing! However, I feel vindicated today after taking this 5 minute web test for facial recognition and passing it with a grade (11 out of 15) that makes me a potential “super recognizer.” 🙂 The researchers at University of Greenwich asked me to follow up by taking a 45 minute test to verify my superior abilities, but I am going to quit while I’m ahead.
If you flunk this facial recognition test, you suffer from “prosopagnosia”—that would not be good because it indicates a poorly developed “fusiform” in the back of your brain. 🙁
For those who do qualify in the UG web quiz and take the longer test, the payoff could be a job with the crack team of super-recognizers at Scotland Yard. Read about them in this fascinating National Geographic post with the Gory Details on “Face Finding Superpower for Fighting Crime”.
Fewer kids, more pets—what this world is coming to
Posted by mark in Consumer behavior, pop on August 28, 2015
NBC’s Today show posted this album yesterday of an Australian dog named Humphrey posing as a newborn baby. Unbelievable! This is what the world is coming to—far fewer children and many more animals being welcomed to families.
The latest issue of Bloomberg Businessweek tells this story of a German pet store with a quarter of a million animals—the world’s biggest—to meet the ever-growing demand of empty nesters. I cannot decide what fascinates me more, the video of 32 weird animals for sale, or the “They Never Talk Back” graphic showing how many countries everywhere have increased per capita spending on pets. The United States leads the way with an arrow point well past $120 per person spent on their loved ones, that is, household animals.
“After food, clothing and medicine, the fourth item is cosmetics and the fifth is pets. That’s serious.”
–Pope Francis