Posts Tagged science
Statistics-driven scientific methods slammed again
This December 13 article published by The New Yorker adds fuel to fire for deemphasizing significance testing as the criterion for accepting purported advancements in science. It’s well worth reading for anyone with a stake in statistics, despite raking over the same coals seen in this March 27 Science News article, which I discussed in a previous blog.*
“A lot of extraordinary scientific data are nothing but noise.”
– Jonah Lehrer, author of “The Truth Wears Off: Is there something wrong with the scientific method”
Evidently much of the bad science stems from “significance-chasers” – those who hunt out findings that pass the generally-accepted p-value of 5% for hypothesis testing. Unfortunately a statistically-significant outcome from an badly-designed experiment is of no value whatsoever.
PS. I credit blogger William Briggs for bringing this article to my attention. His attitude is provided succinctly by this assertion: “Scientists are too damn certain of themselves.”
*Misuse of statistics calls into question the credibility of science March 28, 2010.
Quantifying statements of confidence: Is anything “iron clad”?
Posted by mark in Basic stats & math, Uncategorized on August 19, 2010
Today’s “daily” emailed by The Scientist features a heads-up on “John Snow’s Grand Experiment of 1855” that his pioneering epidemiology on cholera may not be as “iron clad” as originally thought. A commentator questions what “iron clad” means in statistical terms.
It seems to me that someone ought to develop a numerical confidence scale along these lines. For example:
- 100% Certain.
- 99.9% Iron clad.
- 99% Beyond a shadow of a doubt.
- 95% Unequivocal.
- 90% Definitive.
- 80% Clear and convincing evidence.
- 50% On the balance of probabilities.
There are many other words used to convey a level of confidence, such as: clear-cut, definitive, unambiguous, conclusive. How do these differ in degree?
Of course much depends on how is making such a statement, many of whom are not always right, but never in doubt. ; ) I’m skeptical of any assertion, thus I follow the advice of famed statistician W. Edwards Deming:
“In God we trust, all others bring data.”
Statistics can be very helpful for stating any conclusion because it allows one to never have to say you are certain. But are you sure enough to say it’s “iron clad” or what?
Reaching your boiling point
Our marketing director emailed me this motivational video called “212° the extra degree.” this motivational video called “212° the extra degree”. It says that at this temperature water boils providing the steam needed to accomplish things. The idea is that only one degree of heat makes all the difference.
I get it. However, being a chemical engineer with an interest in being accurate about physical processes, I had to be troublesome by pointing out that here in Twin Cities at over 800 above sea-level the pressure drops enough that on average the boiling point drops to 210.5 F. But setting this aside and focusing only on the 1 degree between water and steam, one must keep in mind the huge difference of simply heating up water versus making it change state, the is, the heat (or enthalpy in technical terms) of vaporization.
Thank goodness that our marketing director had become accustomed to working with a bunch of engineers, statisticians and programmers who, when one asks “Could I talk with your for a minute?”, immediately set the timer on their digital watches for precisely 60 seconds (the the nearest one-hundredth).
Coincidentally, while vacationing in Wisconsin’s Door County, I enjoyed a fine demonstration of how hard it can be to bring a quantity of water to a boil. It’s a tradition there to throw a bunch of fish in one kettle and vegetables in another and cook them up with a wood fire. However, as I learned and experienced from a somewhat dangerous vantage point, a pitcher of kerosene provides the final heat needed to accomplish the boil-over. My eyebrows needed a bit of burn-back, so that’s OK.
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.
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.
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
Running hot and cold in Apalachicola – steaming to cook clams and steaming to make ice
My wife and I are celebrating our 35th anniversary with a Thanksgiving week getaway on the panhandle of Florida. Later today we will enjoy a southern version of the traditional banquet, this one will featuring all sorts of grits – the chef’s specialty. I expect some oysters too – mainly harvested just down-beach at Apalachicola. Also, at the local Piggly-Wiggly I noticed lots of sweet potato pies laid out, along with pecan pies, of course. If I lay off the grits, maybe I will keep some room for a piece of the pecan pie, preferably with some whipped cream on top.
Earlier this week we stopped by an interesting museum in Apalach’ (as the locals refer to it). It celebrates the achievements of a local physician, John C. Gorrie, who invented the ice-making machine. He is also considered to be the father of refrigeration and air conditioning. Obviously the folks here in Florida hold Dr. Gorrie in high esteem for his dedication to cooling things off. What interests me, being that I am a chemical engineer, is how steam powered Gorrie’s ice machine. That seems very counter-intuitive, but the thermodynamics are explained nicely here by the inventor:
“If the air were highly compressed, it would heat up by the energy of compression. If this compressed air were run through metal pipes cooled with water, and if this air cooled to the water temperature was expanded down to atmospheric pressure again, very low temperatures could be obtained, even low enough to freeze water in pans in a refrigerator box.”
For a picture of what he patented in 1851 and historical background, see this Wired magazine article by Randy Alfred.
Getting back to the Thanksgiving feast this afternoon and thinking about the oysters, I suppose we will be given a choice of raw ones laid out on ice (thanks to the local inventor) or one cooked with steam. Coming from the middle of our continent, it may be too much of a stretch to eat uncooked shellfish. In fact, it makes me a bit queasy just thinking of it. Although I fancy myself an experimentalist, sometimes I must draw a line in the sand.
PS. One thing I find curious is that the oystermen (sorry ladies) still do their harvesting the old-fashioned way with tongs – see this video, for example .
Math messed with future astronaut’s mind and made him think faster
Last Thursday I enjoyed an inspirational speech by USAF Lieutenant Colonel Duane “Digger” Carey – a Saint Paul guy like me, but one who went far further than possibly any other from our home city. Digger was invited by the University of Minnesota’s Institute of Technology to speak about his experiences as pilot of the Columbia Space Shuttle mission of March 1-12, 2002,* that successfully upgraded the Hubble Space Telescope.**
Although Digger has many stories to tell, not the least of which is his record as a combat fighter pilot, he is most passionate about the benefits of math and science. He feels that his Masters in Aeronautical Engineering, while not directly relevant to flying a jet, enabled him to solve mission-critical problems at afterburner speed.
It was great seeing a hero like Digger Carey talk up math and science to our young people. I recall taking a summer physics camp and working out the equations for rocketry while building a model of the Saturn V. At the end of the course we blasted it off with 5 solid-propellant engines. Unfortunately it went way up and out of sight, so we never recovered the parachuted parts that floated somewhere back to Earth. However, even if we’d found the rocket, there would be no way to recapture the joy of seeing math and science put into action on that first launch. Anyways, that was enough for me. Imagine actually being inside a rocket blasting off! That takes a lot of courage and faith in technology.
“The most important thing we can do is inspire young minds and to advance science, math and technology education.”
— John Glenn, one of NASA’s original astronauts
* The last mission before the disaster of 2003
**See these spectacular new images from Hubble produced by the space telescope after the latest (and likely last) upgrade made by Shuttle Discovery astronauts who just landed Friday.
Quest against greenhouse gases takes on religious fervor
(For the record, I do not drive an SUV, my furnace is a high-efficiency gas burner, my windows are double-insulated and the attic was recently blown with ultra high r-value fill. In other words, please do not question my dedication to reduce fossil fuel use by any reasonable means. Furthermore, I enjoy hiking, biking, canoeing, ice and roller skating — any outdoor activity that does not involve an engine. In other words, I am in favor of environmental protection.)
Tuesday night, at my brother-in-law’s invitation, I listened to a lecture by a professional from the Minnesota Pollution Control Agency (MPCA) who added fuel to the fire for reducing carbon dioxide and other greenhouse gases. The venue was the men’s club for a local Methodist church. The talk was introduced with an appeal for environmental stewardship as a Christian mission. It began with an explanation of the science behind greenhouse gases. To be fair, the speaker suggested that without any carbon dioxide, we would likely be a bit chilled — perhaps by 60 degrees Fahrenheit! Next we saw the usual graphics on global warming over the the past century and back to the Middle Ages (for example, see this site by Woods Hole Research Center (protecting the integrity of the global evironment). Several people then pitched in with comments about how Al Gore dramatized this in the movie “An Inconvenient Truth” by climbing up a ladder to the peak of temperature. (I am suspicious of politicians and Hollywood actors preaching science, so this film remains unscreened.) One fellow, a retired PhD scientist, had the temerity to speak up that the connection of carbon dioxide to global warming is not yet proven and that other causes, not manmade, could have far greater impact on temperature increases or decreases. Seeing others in the audience squirm uncomfortably and even make faces to indicate how crazy this was, I knew that the earth’s fate was sealed — we are soon to be cooked in an atmospheric stew of our own making. The speakers then broke the church members into small groups to select from a handout of action items some things they would pledge to do (see the MPCA’s “What Can We Do”). I am thinking about buying a bunch of cloth bags to bring my groceries home (one of the items). I’ve already done most everything else on the list.
What worries me more than global warming itself is the intermingling of politics and religion with climatology, for example the demands of a group led by Reverend Rich Cizik of the National Association of Evangelicals and Nobel laureate Eric Chivian of Harvard to make changes in values, lifestyles and public policy to avert global warming. Cizik told a news conference that “…Evangelicals have a responsibility to be even more vigilant than others. We will not allow the Creation to be … destroyed by human folly.” An opposing view is offered by Massachusetts Institute of Technology atmospheric scientist Richard Lindzen — a critic of California’s proposed legislation against global warming: “It’s kind of pathetic because we have almost no understanding of major changes in climate over hundreds of thousands and millions of years…we’re forecasting climate when our success in explaining it is about zero.” (Source: CBS Broadcasting .)
Seeing the recent California freeze play havoc with citrus must give that state’s citizens pause in their rush to join the global-warming evangelists.