Glass-shattering interaction of factors
Posted by mark in pop, Uncategorized on December 29, 2012
Last week (12/21) the Today Show broadcasted an alarming demonstration of Pyrex glass exploding after being subjected to certain combinations of conditions. See NBC News’ detailing here . As reported in this American Ceramic Society Bulletin , some scientists believe that changes to the material (replacing borosilicate with soda lime silicate) weakened the glass. However, makers of Pyrex disagree vehemently with these conclusions—see their side of the story here.
It turns out that hot Pyrex pans set directly on a wet or cool surface, such as a granite counter-top, undergo a sudden temperature change that produces some risk of it shattering. That strikes close to home for me, having re-done our kitchen (as is the style nowadays) with granite. Fortunately, being accustomed to plastic (Formica) countertops, I always put down cloth potholders before setting down the hot Pyrex pan. The take-home message is being careful not to subject Pyrex to rapid increases or decreases in temperature. See this site for safety instructions.
PS. On a lighter note (literally: too much sun) regarding heat and silica (main constituent of sand) see this New York Times news making it official that the hottest temperature ever recorded is 134 degrees F in Death Valley. They are pyre Rex.
Correlation of price of wine with the fineness of its taste–an absurd example
Posted by mark in Consumer behavior on December 22, 2012
Behavioral Economics Professor Dan Ariely of Duke University provides an illuminating and humorous example of irrational valuation in his advice column today for Wall Street Journal. It seems that this Christmas holiday weekend may be ruined for a couple who took advantage of a buy-one-get-one-free (BOGO) sale on a fine wine. Actually they paid $17 for one bottle and a nickel ($0.05) for the other. They asked Professor Ariely to help them escape a terrible dilemma: For the holiday party would it be OK to bring the cheap wine? Ha ha!
I hope that for the coming year all of you readers of StatsMadeEasy do not get hung up spurious issues like this relating to correlation and causation or any other statistical kerfuffles. Happy Holidays and New Year!
PS. I leave you with this toast to 2013–a picture taken last week during my tour of a winery in the Colchagua Valley south of Santiago, Chile. Cheers!
Strange times: Ice forming in unlikely places and melting where it shouldn’t
Posted by mark in Nature, Uncategorized on December 9, 2012
My flight yesterday from Minneapolis to Santiago got held up for de-icing. Being so near to the year-end solstice, the change in seasons from Minnesota to Chile could not be more dramatic—a swing of 45 degrees in solar angle relative to the ecliptic plan. So it’s out of snow (storming today back home) and into 80+ degrees and pure sun. : )
Things are wackier than I’d thought in regard to where one might expect to find ice nowadays. For example, who would have thought that water could freeze on Mercury? But that’s what NASA recently reported based on a shout out from their spacecraft Messenger, which detected polar hydrogen via neutron spectroscopy. See the details here. I enjoyed the quip by Sean C. Solomon, the principal investigator for Messenger, about there being enough ice to encase Washington, D.C., in a frozen block two and a half miles deep.* That might be what’s needed to cool down all the rhetoric about the fiscal cliff. 😉
Meanwhile the worries about the warming climate melting Earth’s icecaps just keep coming on. Concerned about contrails contributing to the greenhouse effect, the Washington Post is now demanding the Santa’s sleigh be grounded. Read this 12/4/12 blog and weep. : (
*On Closest Planet to the Sun, NASA Finds Lots of Ice, 11/29/12
The amazing persistence of biased scientific results—Popeye’s spinach found fraudulent
Posted by mark in science, Uncategorized on December 5, 2012
I recently completed a series of webinars on using graphical diagnostics to deal with bad experimental data.* The first thing I focused on was avoidance of confirmation bias – hearing what you want to hear, for example in the persistence of the possibilities of cold fusion. See more cases of confirmation bias in this detailing by Peter Bowditch in Australasian Science.
I came across another interesting example of the persistence of wished-for results in a review** of Samuel Arbesman’s new book on The Half-Life of Facts. It turns out that spinach really does not delivery the amount of iron that my mother always believed would make it worth us eating this horrible food. She was a child of the 1930’s, at which time it was widely believed that the edible (?) plant contained 35 milligrams of iron, a tremendous concentration, per serving. However, the actual value is 3.5 mg—the chemist who first analyzed it misplaced the decimal point when transcribing the data from his notebook in 1870! In 1937 this error was finally corrected, but my mom never got the memo, unfortunately for me and my six younger siblings. ; )
*“Real-Life DOE” presentation, posted here
** The Scientific Blind Spot by David A. Shaywitz in the 11/19/12 issue of Wall Street Journal
Speak softly but carry a big statistic
I heard on CBS Radio radio today this play on Teddy Roosevelt’s famous words. It was quoted by U.S. Senator Amy Klobuchar as her secret weapon (statistics, that is) for women politicians. Searching internet I think it originated from Anne E. Kornblut in her book Notes from the Cracked Ceiling in a section dedicated to Klobuchar. She (the Senator) figures on making an impact on the impasse over the coming “fiscal cliff”. I have no doubt that Senator Klobuchar and scores of other politicians, male and female, will be slinging a lot of statistics during this debate on how to avert financial disaster for us taxpayers. It will take some work to ferret out what’s really true out all the partisan hyperbole.
Statistician mines poll results to come up with odds-on fav for President
CBS News this morning reported the prediction by New York Times statistician Nate Silver on who will be our next President. OK, now that you know (presuming you could not resist following the link), how sure are you that it’s accurate? After all Silver is the author of The Signal and the Noise: Why So Many Predictions Fail – But Some Don’t—published only a month or so ago. My hunch is that Silver does as well as anyone—given so many unknowns that cannot be known, not the least of which is the fickle nature of undecided voters who might en masse switch allegiance the day of the election. Anyways, I am viewing his prediction the same as a weather forecast two days out, that is, with a good deal of skepticism but, nevertheless, appreciation for the science behind the modeling.*
PS. A friend asked me this week whether averaging polls is really valid. I suppose so based on Silver doing it. See how he does it at this detailing by him in his “538” blog (538 is the number of electors in the United States Electoral College).
*For example, within 72 hours of a hurricane’s landfall, meteorologists now predict the bulls-eye within a 100-mile radius—compared to 350 miles 25 years ago. They did really well forecasting Sandy as reported here by The Washington Post.
Probability of vote being pivotal is so small it’s not worth voting
That was the view of 2nd-year PhD student Douglas VanDerwerken up until this Presidential election. He abstained on the basis of the lack of return on investment for spending the time to vote when it really cannot make a difference. VanDerwerken lays it all out for statistics magazine Significance in an article for their current (October) issue.* According to his reckoning, there is less than one chance in a million (4.5×10^-7 to be precise) of any person’s vote having an impact. This would be a situation where the voter lives in a swing State and the election comes to a dead heat.
Fortunately (in my opinion—being one who views it as a civic duty) VanDerwerken had an epiphany based on moral reasons, so he shall vote. Thank goodness!
“If you think about it, voting in a large national election – such as the US Presidential election – is a supremely irrational act, because the probability that your vote will make a difference in the outcome is infinitesimally small.”
– Satoshi Kanazawa, rational choice theorist**
* “The next President: Will your vote decide it”
**See Kanazawa’s three-part series on “Why Do People Vote” for his blog “The Scientific Fundamentalist” hosted by Psychology Today. Start with Part 1 posted here and continue on to the end for the answer.
Time to lighten up on homework?
Posted by mark in pop, Uncategorized on October 21, 2012
The Wall Street Journal’s Market Watch this Friday posted the data shown in this chart. For the 11 countries shown** you can see why WSJ seconds the call by French President Hollande to ban all homework.
Students would party hearty but this laissez-faire approach will not fly with those blessed with ambitious parents. Nevertheless the call for less homework, fueled by new data from the National Center for Education Statistics, reinforces other studies going back at least a decade.
It will be interesting to see what emerges as a consensus for a the happy medium on amount of homework assigned. Four hours per night seems way too much, especially at the 8th grade level.
Meta-analysis of hundreds of studies done on the effects of homework shows that the evidence supporting the practice is, at best, modest. Homework seems to be most useful in high school and for subjects like math. At the elementary school level homework seems to be of marginal or no academic value.
– Malcolm Gladwell
*See the report here
**I took out Saudi Arabia, whose result of 34% below average, given 11% being assigned over 4 hours of homework per night, fell far below even these very off-putting predictions–an outlier statistically.
Acknowledgment: Thanks to Devan Govender for alerting me to this issue.
USA unemployment statistic creates a sensation
“Unbelievable jobs numbers..these Chicago guys will do anything..can’t debate so change numbers.”
– Jack Welch
Thursday morning I attended a briefing on the economy by an expert from Wells-Fargo bank. Looking over the trends in USA unemployment rates he noted that no incumbent since World War II has achieved re-election when joblessness exceeded 8 percent. Friday the Bureau of Labor Statistics (BLS) announced that the the national unemployment rate is now 7.8%, an improvement from 8.1% last month. How accurate is this number and is it precise enough that a 0.3% difference can be considered significant? I agree with the conclusion of this critique posted by Brookings Institution that “a large part of monthly unemployment fluctuations are spurious.” So, really, all this fuss about it being 8.1 versus 7.8 percent is really silly from a statistical point of view. However, it is entertaining!
Rock on with algorithms?
Posted by mark in pop, Uncategorized on October 2, 2012
I started off my career as an experiment designer before the advent of cheap calculators. Paying $400 for an HP unit that (gasp!) did logarithms went far beyond my wherewithal in 1974. That was roughly the tuition for one college quarter at University of Minnesota if memory serves. I managed to cover that cost plus room and board by working 24 hours a week washing pots and pans at a hospital kitchen. Those were the days!
Calculating effects from the two-level factorial designs I did that summer as an intern at a chemical research lab required a lot of hand calculations—many numbers to add and subtract. Thankfully a fellow named Yates developed an algorithm after these experiments were invented in the 1930s. Following his directions one could tally things up and even do check sums without having to think much. That’s what algorithms do—provide a recipe for solving problems.
As an engineer I have a healthy respect for algorithms, but my wife, who works as a preschool teacher, thinks this is geeky. For example, I admired the nerdy professor in the TV show “Numbers” that aired a few years ago. But every time he expounded on some algorithm that ingeniously saw the pattern of a serial criminal, she just laughed. Ironically she is now hooked on a show called “Person of Interest” that is based on predictive policing, that is, using algorithms to calculate a crime to come. That scares me!
According to a new book by Christopher Steiner titled Automate This: How Algorithms Came to Rule Our World (see this Wall Street Journal review) all of us had best be on our guard against seemingly clever ways to systematically solve problems. It seems that the engineers, mathematicians, programmers and statisticians who come up with these numerical recipes invaded Wall Street. They became known as the “Quants”—dominating the way stocks now get traded.
The problem with all this (even I have to admit) is that these systematic approaches to things take all the fun out of making choices. Do we really want algorithms to pick our soul mates, invest our money, etcetera? I am up for algorithms like Yate’s that quickly solve mathematical problems. A good example of this is the first known algorithm recorded on clay tablets in 2500 B. C. that helped Sumerian traders divvy up a given amount of grain equally to a varying number of recipients. However when things become capricious with many unknowns that are unknowable being thrown into the mix, I’d rather make my own decisions guided by wise counsel.
There is an elephant in the room whenever it comes to discussing computer algorithms, particularly highly automated ones. Almost all such algorithms are inaccurate. They are inaccurate for many reasons, the most important of which is that human behavior is fickle. The inaccuracy could be shockingly high.
– Kaiser Fung, author of Numbers Rule Our World
I really shouldn’t bring this up, but do you suppose certain politician might be spending a lot of money on algorithmic solutions to how they can win election? Do these algorithms have any qualms about turning their protagonists into nabobs of negativism? I do not believe that an algorithm has any heart, unfortunately. An algorithm is like Honey Badger—it just don’t care.