Chance News 89

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Quotations

"To rephrase Winston Churchill: Polls are the worst form of measuring public opinion — except for all of the others."

--Humphrey Taylor, Chairman of The Harris Poll, Letter to the Editor, New York Times, 24 October 2012

Forsooth

Simpson's paradox on Car Talk

Take Ray out to the ball game...
Car Talk Puzzler, NPR, 22 September 2012

Popeye batted .250 for before the All-Star break, while Bluto batted .300; Popeye batted .375 after the All-Star break, while Bluto batted .400. How did Popeye win his bet that he would have the better average for the season? Statistically minded listeners will quickly recognize this as an instance of Simpson's Paradox. Still, everything sounds like more fun when Tom and Ray discuss it! You can read their solution here.

A famous real-life example of Simpson's Paradox with batting averages can be found here.

Sleep and fat

Your fat needs sleep, too
by Katherine Harmon, 60-Second Health, Scientific American, 16 October 2012

As described in the article (actually the transcript from a podcast; you can listen fratom the link above):

Sleep is good for you. Getting by on too little sleep increases the risk for heart disease, stroke, high blood pressure, diabetes and other illnesses. It also makes it harder to lose weight or stay slim because sleep deprivation makes you hungrier and less likely to be active during the day.

Further,

Now, research shows that sleep also affects fat cells. Our fat cells play an important role in regulating energy use and storage, including insulin processing.

The research referred to, a randomized crossover study, can be found in an article by Josiane Broussard et al. Its full title is “Impaired Insulin Signaling in Human Adipocytes After Experimental Sleep Restriction: A Randomized, Crossover Study.” Scientific American says

For the study, young, healthy, slim subjects spent four nights getting eight and a half hours of sleep and four nights getting only four and a half hours of sleep. The difference in their fat cells was startling: after sleep deprivation, the cells became 30 percent less receptive to insulin signals—a difference that is as large as that between non-diabetic and diabetic patients.

Discussion

1. The Scientific American article fails to mention the number of subjects: “1 woman, 6 men” or two more than the number of authors of the study. The lone female, “participant 6,” had four of her sixteen data points missing.

2. The entire study was carried out at one institution. Why might this be a problem?

3. An extended, positive editorial commentary in the Annals of Internal Medicine refers to Aulus Cornelius Celsus who

argued in favor of “restricted sleep” for the treatment of extra weight…it seems that Celsus may have been wrong: He should have argued in favor of “prolonged sleep” for the treatment of extra weight.

Look up who Celsus is and why his pronouncements about medical matters might be suspect. Then determine why the commentator claims that the authors “deserve commendation for a study that is a valuable [statistically sound] contribution” to the role of sleep in human health.

4. As indicated above, each of the subjects were young, healthy and slim. Why is this uniformity good statistically? For inference purposes to a larger population, why is this uniformity not so good statistically?

Submitted by Paul Alper