Difference between revisions of "Chance News 114"

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The everyday language used to describe probabilities is notoriously vague.
 
The everyday language used to describe probabilities is notoriously vague.
  
===Chance of rain==
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===Chance of rain===
 
[https://www.kvia.com/news/what-does-a-chance-of-rain-in-the-abc-7-day-forecast-really-mean-/775928797 What does a chance of rain in the ABC-7 Day forecast really mean?] <br>
 
[https://www.kvia.com/news/what-does-a-chance-of-rain-in-the-abc-7-day-forecast-really-mean-/775928797 What does a chance of rain in the ABC-7 Day forecast really mean?] <br>
  
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<blockquote>
 
<blockquote>
 
"The chance of rain, or probability of precipitation (POP), is based on a mathematical formula that takes the forecaster's confidence into account." That formula is as follows: POP = Coverage x Confidence.  
 
"The chance of rain, or probability of precipitation (POP), is based on a mathematical formula that takes the forecaster's confidence into account." That formula is as follows: POP = Coverage x Confidence.  
 +
</blockquote>
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But the following interpretation is offered.
 +
<blockquote>
 +
These words are also associated with a Pop:
 +
<br>
 +
10-20% includes "slight chance" and "widely scattered"
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<br>
 +
30-50% includes "chance" and "scattered"
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<br>
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60-70% includes "likely" and "numerous"
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<br>
 +
80-100% includes definitive types of precipitation such as rain, snow or showers.
 
</blockquote>
 
</blockquote>
  

Revision as of 15:37, 4 September 2018

July 1, 2018 to ...

Quotations

"I have found it intriguing to narrate the history of statistics as viewed from the special lens of its orphaned sister: causation. The story of this 'forbidden love' was never told before and, believe me, it is full of mystery, intrigue, personalities, dogmatic orthodoxy, and heroic champions of truth and conviction."

-- Judea Pearl, in an interview with ASA Executive Director Ron Wasserstein, AmStat News, 1 August 2018

[Vermont state] Rep. Van Wyck of Ferrisburgh explained his vote as follows: “Madam Speaker: I voted No. In college, I learned there were Lies, Damnable Lies, and then there is Statistics. I am not impressed with a number of these statistics.”

-- in: Journal of the House, 1 May 2018

Submitted by Jeanne Albert


"But claiming there is no ‘safe’ level [of alcohol comsumption] does not seem an argument for abstention. There is no safe level of driving, but government do not recommend that people avoid driving. Come to think of it, there is no safe level of living, but nobody would recommend abstention."

-- David Spiegelhalter, quoted in: No safe level of alcohol consumption, major study concludes, The Independent, 24 August 2018

Forsooth

“That means then that criminal aliens are committing 28 percent of the crimes in the United States. And so that means 28 percent of the murders, 28 percent of the rapes, 28 percent of the violence and the assaults and battery, first- and second-degree murder and also manslaughter attacks are committed by criminal aliens.”

-- Representative Steve King (R-Iowa), quoted in: Fact-checking President Trump’s numbers on the ‘human toll of illegal immigration’, Washington Post, 6 July 2018

Never too early to start!

Distributions.jpg

Submitted by David Ballard

(Note: It's a real puzzle toy, and apparently sold out!)

How likely is "likely"?

If you say something is “likely,” how likely do people think it is?
by Andrew Mauboussin and Michael J. Mauboussin, Harvard Business Review, 3 July 2018

The everyday language used to describe probabilities is notoriously vague.

Chance of rain

What does a chance of rain in the ABC-7 Day forecast really mean?

We read:

"The chance of rain, or probability of precipitation (POP), is based on a mathematical formula that takes the forecaster's confidence into account." That formula is as follows: POP = Coverage x Confidence.

But the following interpretation is offered.

These words are also associated with a Pop:
10-20% includes "slight chance" and "widely scattered"
30-50% includes "chance" and "scattered"
60-70% includes "likely" and "numerous"
80-100% includes definitive types of precipitation such as rain, snow or showers.

Counting LA's homeless

More sidewalk tents, but fewer people living in them? The 2018 homeless count's new math
by Dakota Smith and Doug Smith, Los Angeles Times, 15 July 2018

Plastic straws

How a 9-year-old boy’s statistic shaped a debate on straws
by Niraj Chokshi, New York Times, 19 July 19 2018

Milo Cress, a nine-year-old Vermont boy, has launched the Be Straw Free campaign. He estimates that Americans use 500 million plastic straws a day, a figure that has been widely reported in the press.

Comment on gerrymandering

Emil Friedman observed that Gerrymandering has been a hot topic in recent Chance News (see, for example, posts in CN 111, CN 112, CN 113), and sent the following comment:

Virtually any complex method we devise to combat Gerrymandering can probably be manipulated to partisan advantage. However, a simple way to make partisan gerrymandering nearly or completely impossible would be a nationwide system wherein we divide each state that is wider than it is tall (on a Mercator Projection) by vertical straight lines into contiguous vertical slices having nearly equal populations. States that are taller than wide would be divided horizontally instead of vertically. If adopted nationwide, it would make it impossible to rig the voting districts. However, a big downside is that it -- and almost any other solution involving a nationwide system -- would probably require a constitutional amendment.

Are college exams killing grandma?

For comic relief as we approach the start of a new academic year, Margaret Cibes sent the following two articles:

The dead grandmother/exam syndrome
by Mike Adams, Annals of Improbable Research, November/December 1999
A preliminary report on an intervention designed to reduce grandmother death resulting from college exams
by Lee Jussim, April 2002

Jussim cites Adams's original paper, where we read

The basic problem can be stated very simply:
A student’s grandmother is far more likely to die suddenly just before the student takes an exam, than at any other time of year.

The paper includes tongue-in-cheek regressions and wild extrapolations to prove the point. Reproduced below is one of the tables which shows mean family death rate (in deaths per 100 students), broken down by students's current grade and whether an exam (midterm or final) is coming up.

Grandma.png

Alzheimer's drug study

Why the latest Alzheimer’s drug study has so many people confused
by Clifton Leaf, Fortune, 30 July 2018

Examines conflicting reports in the popular press concerning a recent Alzheimer's drug study; For example, see the following stories:

Further discussion at HealthNewsReview.org, which asks why the drug generated so much news coverage.

Workplace wellness programs

Workplace wellness programs don’t work well. Why some studies show otherwise
by Aaron E. Carroll, New York Times, "TheUpshot" blog, 6 August 2018

Compares results of observational studies with subsequent randomized trials. In a number of cases, the effects found in the earlier studies are seen to disappear. Article includes the following graphic:

IllinoisWellness.png

At HealthNewsReviews, Gary Schwitzer's post Observations about today’s observational studies in the news identifies three misleading news stories from August 28, 2018.


Alcohol risks

How much alcohol is safe to drink? None, say these researchers
by Nicholas Bakalar, New York Times, 27 August 2018

Study causes splash, but here’s why you should stay calm on alcohol’s risks
by Aaron E. Carroll, New York Times, "TheUpshot" blog, 28 August 2018

The articles refer to a study published in the Lancet , entitled "Alcohol use and burden for 195 countries and territories, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016." The researchers write

Alcohol use is a leading risk factor for global disease burden and causes substantial health loss. We found that the risk of all-cause mortality, and of cancers specifically, rises with increasing levels of consumption, and the level of consumption that minimises health loss is zero. These results suggest that alcohol control policies might need to be revised worldwide, refocusing on efforts to lower overall population-level consumption.

Moreover, as the first NYT article notes, the study did not find any health benefits from moderate drinking, which runs counter to some previous thinking.

David Spiegelhalter (see Quotations above), was critical of the study's advice for moderate drinkers. In a blog post he reproduced the following graphic from the Lancet.

Alcohol risks.jpeg

Notice that the change from 0 to 1 drink per day is barely visible here. Moreover, while the paper focused exclusively on relative risks, Spiegelhalter applauds the Lancet editors for including absolute risks in the press release, which he quotes as follows.

Specifically, comparing no drinks with one drink a day the risk of developing one of the 23 alcohol-related health problems was 0.5% higher — meaning 914 in 100,000 15–95 year olds would develop a condition in one year if they did not drink, but 918 people in 100,000 who drank one alcoholic drink a day would develop an alcohol-related health problem in a year.

This increased to 7% in people who drank two drinks a day (for one year, 977 people in 100,000 who drank two alcoholic drinks a day would develop an alcohol-related health problem) and 37% in people who drank five drinks every day (for one year, 1252 people in 100,000 who drank five alcoholic drinks a day would develop an alcohol-related health problem).

This calculation was also reported in the second NYT article, which noted, "Even at five drinks per day, which most agree is too much, the vast majority of people are unaffected." That article also notes that the study is not a controlled experiment, but rather a large meta-analysis of observational studies. Thus, despite the researchers's best effort, there is no guarantee that all possible confounding variables have been accounted for. The article cites an NCBI study The perils of conducting meta-analyses of observational data, writing

But when we compile observational study on top of observational study, we become more likely to achieve statistical significance without improving clinical significance. In other words, very small differences are real, but that doesn’t mean those differences are critical.