An Easter experiment for those who still believe a bunny bears eggs* *(Beware of the green ones!)
Today’s Saint Paul Pioneer Press “Bulletin Board” provides an idea on how to provide some added delight for any children who still believe in the Easter Bunny: Have them plant one of their jelly beans, then watch for it to grow into a lollipop. Doesn’t that sound like a fun experiment!
By the way, be careful with the green jelly beans – they cause acne (p<0.05) according to this exhaustive statistical-study of every available color.
Winter not loosening its icy grip on Spring
I woke up to snow yesterday morning. It couldn’t quite cover the greening grass underneath, nor did it seem to discourage the budding bushes. Today the snow has disappeared and the near 40 degree F temperature seems mild with the power of April’s sun and the abatement of fierce northern winds. However, our Canadian neighbors are not faring quite as well, as evidenced by this very cool (literally and figuratively) photo from my sister – a resident of Calgary. Notice how the snow fingers feature icy nails — chilling!
When will Winter finally loosen up and let Spring spring free, eh? Maybe May…
Armed and dangerous – switchblades and statistics
Posted by mark in Basic stats & math on April 11, 2011
(Warning: Quirky material ahead =>)
Seeing this CBS News about Maine legalizing switchblades for one-armed people reminded me of a riddle about limbs that’s posed by some statisticians for educational purposes. Here it is: “The great majority of people in [fill in your country here] have more than the average number of [choose either arms or legs here].”
For an answer {UK, legs}, see this posting on averages by Kevin McConway, Professor of Applied Statistics in the Department of Mathematics and Statistics at The Open University. I heard this riddle also from Hans Rosling in his BBC TV program on “The Joy of Statistics.”* He spoke of his home country of Sweden, whose inhabitants on average have 1.999 legs.
I’m quitting while I’m ahead. Oops, this makes me wonder if I have an average number of heads – a scary thought, my hunch being that I’m below average for this. I never imagined that averages could be so creepy!
*See this StatsMadeEasy blog on Rosling
Supreme Court overturns tyranny of statistical significance
In today’s Wall Street Journal, The Numbers Guy (Carl Bialik) reports on a unanimous ruling by the Supreme Court that companies cannot hide behind statistical significance (lack thereof in this case) as an excuse for nondisclosure of adverse research. He passes along this practical advice:
“A bigger effect produced in a study with a big margin of error is more impressive than a smaller effect that was measured more precisely.”
— Stephen Ziliak, economics professor
However, this legal analysis of the ruling cautions that statistical significance remains relevant for assessing materiality of an adverse event.
Given all this, we can be certain of only one thing – more lawsuits.
First signs of Spring – premature return home by robins
As you can see from this photo taken Friday while cross-country skiing, Spring has not sprung in my neck of the woods. However, just overhead as I took this shot were several dozen robins perched in the birch. They were chattering a great deal – I imagine in complaint about which bird brain thought it was time to migrate back north.
A couple of years ago at this seasonal juncture I wrote about phenology – the study of timing for nature’s ways. For us in Minnesota the robins’ arrival is a sure sign of warmer weather around the corner.
Having just returned from a Spring break in Florida, I wondered how these southerners can detect seasonal changes. My searching on internet reveals little, other than this announcement of the first phenology workshop in Florida in 2009. The one sure sign of Spring for Floridians is the hordes of Minnesotans coming down for a break. They probably trump anything more subtle from Mother Nature.
Bubbly graphs make statistics delightful
Check out this link* to an interview by Fareed Zakaria of “gap minder” Hans Rosling. This Swedish statistician, with a focus on global health, uses dynamic bubble graphs to dramatize world developments that are closing the gap to USA’s lead in well-being.
It really is mesmerizing to see Rosling dramatize statistics via his moving graphs. See his recent hour-long BBC special “The Joy of Stats” at this GapMinder website. You will find it very entertaining and enlightening, I am sure.
“I kid you not – statistics is now the sexiest subject around.”
– Hans Rosling
Fortunately for all of us, Google bought the technology for these motion charts to make them widely available. For example, fiddle with the graph correlating life expectancy and fertility at this Google Labs’ Public Data Explorer posting.
Who would have ever thought that statistics could be so much fun!
*Thanks to Paul Sheldon, an independent consultant specializing in quality and productivity tools, who provided me the heads-up.
Beware of 5th poly mole!
I found it amusing that, when forced to try modeling my weight data (see previous blog), my DOE software recommended a fifth order polynomial* model! That’s a bit more ‘tayloring’ (Ha ha – inside joke) than I really needed. In fact, just to show how silly this is (5th order!) I offer the following scenario as a cautionary tale. Perhaps it may help to dissuade others who make similarly nonsensical models from what is really just (naturally) randomly generated data.
Looking forward to a work/vacation trip to Tampa in late March (I really will be going there, I am happy to say!), let’s pretend that I use this fifth-order model to help me decide whether to bring a swimming suit. Hmmm, extrapolating out to day 75, when I finish my conference and head for the Gulf shore, the over-fitted model (really should just use the mean!) predicts that by then I will balloon to nearly 100 pounds over my norm. In this case I may easily be mistaken for a beached whale!
It’s just not right to apply model-fitting tools to what is not a DOE, but rather simply a process run-out at steady-state conditions. Extrapolation makes this even more dangerous by far. See the graph for a case in point.
*(A math-phobic person I am acquainted with, whom I will not identify, mockingly refers to these equations as “poly moles” — hence my title for this blog.)
“Welcome, Body Mass seeker”
Posted by mark in Uncategorized, Wellness on February 27, 2011
This is the greeting from Steve Halls, MD, at his web weight-calculator. After a fair amount of searching on the internet, I found this site on body-mass the easiest to use and informative. However, I cannot speak on its accuracy. I will only admit that it provided far less scary news (and realistic, I feel) about my own weight than other websites giving advice on this vital subject.
According to the “updated hall.md v2” standards, I am “marginally overweight” at the 53rd percentile of other American males at my age and height. As we like to say in Minnesota, this could be worse, so it’s not so bad.
Discussing what should be the “ideal” weight would take up a great deal of time and energy: Never mind that. What I want to do is focus on monitoring weight. For example, I just completed the pictured outlier-detecting run-chart* on my 20 weighings** thus far this year. Notice that none of the results fall outside of the 95 percent confidence limits.
Even so, after I penciled in my number for the highlighted point, my wife hassled me a bit about going overweight when she saw . I predicted that she would see a regression to the mean, which didn’t impress her one bit. Nevertheless, the value of being patient by charting data over a period of time can be seen in this instance – it vindicates me not reacting to one result.
Coincidentally, our contract trainer Doug Hubbell came to Minneapolis for our new Advanced Formulations workshop. He is the author of a handbook for managers seeking quality improvement (Managing for Profits – to be published soon). Doug is a plain-talking straight-shooter who rifles in on what’s needed to stop chronic manufacturing waste. Charting is a powerful part of his arsenal of quality tools. His reaction to me mentioning my monitoring of weight was “I hope you do not expect this chart to help you lose pounds.” Naturally I wouldn’t admit to that, but, honestly, it did cross my (hopeful!) mind. However, I am mainly just trying to track a very gradual increase of about 1 pound per year since my high-school graduation, when I was in the best shape of my life.
The battle against the bulge continues…
*Using Design-Expert® software’s diagnostics tools. I focused on a chart that deletes each point before calculating its deviation in terms of standard deviation, which makes it more sensitive to statistical outliers. For details, see this Wikipedia entry on Studentized residual (it explains internal and external methods).
**Done with a new bathroom scale that I really like – this Precision Digital model by EatSmart.
Fun graphs and charts on names: How popular is yours and where is it populated?
My latest issue of National Geographic came with this fascinating mapping of population by surname. Seeing “Anderson” looming large over Minnesota did not surprise me, but I didn’t realize how many of us “snow birds” had permanently escaped to California. Take a look and see if you can locate any of you long-lost wander-kin around the USA.
The Junk Charts blog, one of my favorites, gave a generally favorable review of the “Nat-Geo” name chart, but they recommended an even-better one – the Baby Name Wizard, which plots the popularity of first names over the last 130 years.
I am expecting my first grandchild this summer, so there’s been lots of talks about names lately, thus this statistical chart caught my eye. You, too, may find it interesting. I suggest you start by hovering mouse over the widest streams (blue for boy, pink for girl) at the left (John, Mary, etc)* and then see how their popularity changes over the past 130 years. A tip: Click the graph to see trends for any given name, or enter it directly. Press “x” to get out of any specific name field (or type in another). I typed in my name and saw an explosion of popularity in mid-20th century, but now it’s fading away. The same holds true for my sister Nancy and my wife Karen – we all get tagged as baby-boomers straight away.
If you think there’s any chance of your name ranking in the top 1,000 for popularity in the USA at any time since 1880, type it in. How do you do, _______ (<= name here)?
Self-proclaimed lottery expert advises gamblers to never pick numbers that won before
Posted by mark in Consumer behavior on February 13, 2011
Recently I heard a local talk-show host interview Richard Lustig, author of Learn How to Increase Your Chances of Winning the Lottery.* His first suggestion was to never pick a number that won a prior lottery drawing. That led to lots of discussion by callers – mostly skeptical. Evidently this belief that previously non-winning numbers become “due” is widespread, so much so that it’s become known as the gamblers fallacy.
“Lottery: A tax on people who are bad at math.”
– Ambrose Bierce
PS. Did you hear about the wannabe-winner of the lottery who prayed and prayed and prayed to hit the jackpot. Finally an exasperated God responded with this request: “Could you at least just buy one ticket?”
*This paperback book lists for $40 on Amazon, but I will not provide the link because I do not recommend it. However, you may find it amusing to read the customer reviews.