Posts filed under General (3152)

• On herd immunity, from Quanta magazine “The necessary level of immunity in the population isn’t the same for every disease. For measles, a very high level of immunity needs to be maintained to prevent its transmission because the measles virus is possibly the most contagious known organism.”
• Pornhub, as is its habit, has an interesting graph on what the Hawai’i missile false alarm did to its workload (not very NSFW, but Pornhub)
• From NPR For Now, Sequencing Cancer Tumors Holds More Promise Than Proof.  Even though the story is about how DNA sequencing of tumors hasn’t been a very successful strategy so far, they lead with a ‘miracle cure’ story, because that’s how the news works.
• “Bad Graphics: manipulation or laziness” from David Spiegelhalter, talking about an example from the Daily Mail.
• Also from David Spiegelhalter: there’s a recent research paper on correlations between alcohol consumption and dementia. The researchers said ““Consuming more than one UK standard unit of alcohol per day is detrimental to cognitive performance and is more pronounced in older populations”, which was widely reported in the media. This is their graph of their analysis. The minimum of the graph is at 16g/day: two UK units or 1.6 NZ units.
  
  If we could trust this model, it would actually say consuming less than one unit per day is detrimental.
• Via Elaine Smid, the  title and abstract of a research paper
  

• Metropolitan Museum of Art President “For various reasons, over the past 10 or 12 years, the pay-as-you-wish policy has failed. It has declined by 71% in the amount people pay.” Felix Salmon “It’s worth fact-checking this, because it turns out that it’s not really true”
• Cloudflare, a company that distributes websites across the world, has a wall of lava lamps that it uses for random number generation (presumably to seed computational pseudorandom generators)
• “Do algorithms reveal sexual orientation or just expose our stereotypes?”— on last year’s ‘gaydar’ paper.
• 538 looks at how they got an analysis of broadband internet availabilty wrong, due to bad data.
• “The projects tried to show hidden patterns of our daily shopping….Unfortunately, it shows only the internal categorization and sorting of the supermarket.” Another example of data not meaning what you think it means. Christian Laesser (via FlowingData)
• “Child protective agencies are haunted when they fail to save kids. Pittsburgh officials believe a new data analysis program is helping them make better judgment calls.” from the New York Times.
• The NZ government has released a review of the handling of weather data (PDF)
• From the LSE Impact blog “Academics looking to communicate the findings and value of their research to wider audiences are increasingly going through the media to do so. But poor or incomplete reporting can undermine respect for experts by misrepresenting research, especially by trivialising or sensationalising it, or publishing under inappropriate headlines and with cherry-picked statistics.”  As StatsChat readers will known a lot of this is public-relations people, but some of it is definitely the researchers.
• The scientific reporting of some pre-clinical research is disturbingly crap: a report in the BMJ; Siouxsie Wiles commenting at The Spinoff
• Constructing optical illusions for AI visual systems: (gory technical details)
• You may have seen reports of research saying that Australian hawks spread bushfires…

The theme of the paper is literally “we should pay more attention to Indigenous knowledge” but somehow in translation it’s become “LOL hawks are mad”

— David Fickling (@davidfickling) January 10, 2018

• “Every now and then a story appears in the media about how boffins (and it is always “boffins”) have worked out an equation for something: the perfect cup of tea, the most depressing day of the year, the best way to make pancakes, the perfect handshake, or in the most recent case, the perfect cheese on toast.” The equation for the perfect bullshit equation.
• The BBC’s statistics-in-the-media radio program More or Less has a special ‘statistics of the year’ episode
• Some interesting student projects from a data visualisation class
• How Spotify picks your music.
• “Average London”: averages of tourist photos of the same London attraction.
• Displaying uncertainty in the UK unemployment rate
• One of the problems in training modern neural network classifiers is that they will pick up on anything, sensible or not. Luke Oakden-Rayner writes about a popular set of data from chest x-rays and why it won’t teach the computers the right things.
• The American Academy of Family Physicians is not endorsing new blood pressure standards that would increase the proportion of US adults defined as having hypertension from about 1/3 to about 1/2.

Part of the point of mathematical modelling is discarding unimportant features of a problem to make it tractable. But you have to discard the right features. Here are two recent stories about mathematical optimisation.

Jason Steffen has invented a more efficient way of getting passengers on to planes — not just more efficient than what US airlines actually do, but even more efficient than letting passengers board at random. He writes

So, why isn’t this optimum method of airplane boarding being adopted by any carrier in the industry? One significant reason may be the challenge of its implementation — lining passengers up in such a rigid order. 

I’d argue that a much more important reason is you’d have to get rid of priority boarding, making frequent flyers queue with everyone else and depriving them of their chance to get the lion’s share of overhead luggage space.  A model that doesn’t account for the power of frequent flyers is solving the wrong optimisation problem to get implemented.

The same sort of issue often turns up in US discussions of partisan gerrymandering, where you’ll see mathematicians write about algorithms for perfect electorate design. These don’t solve an existing problem, because they don’t take into account who actually draws districts: it isn’t impartial mathematicians.  The main theoretical limitation on gerrymandering in the US is the power of courts to declare a partisan redistricting plan unconstitutional — but they aren’t willing to do so.  Justice Scalia wrote in 2004

    Eighteen years of judicial effort with virtually nothing to show for it justify us in revisiting the question whether the standard promised by Bandemer exists. As the following discussion reveals, no judicially discernible and manageable standards for adjudicating political gerrymandering claims have emerged. Lacking them, we must conclude that political gerrymandering claims are nonjusticiable and that Bandemer was wrongly decided.

There’s a new effort to change this, from Wisconsin. In 2015, the state was sued in federal District Court over its redistricting plan, and lost. The case focused on the ‘efficiency gap’; the difference in the number of ‘wasted’ votes between the two parties (as a percentage of all votes cast). The Supreme Court has heard an appeal in October this year and is thinking about it.

Patrick Honner wrote about the efficiency-gap proposal for Quanta, but there’s a lot more detail in a 2015 expert-witness report by Simon Jackman (PDF), an Australian political scientist at Stanford.

Today, Stuff’s “Well and Good” section has

There’s nothing wrong with the content, which describes some interesting dry sparkling wines one might want to try (if one liked that sort of thing enough to spend that much).  But it’s not a health story.

The very-low-sugar wines differ from ordinary ‘brut’ champagne by less than 10 grams of sugar per litre, in a drink that has more than 120 grams of alcohol per litre.   The sugar in an ordinary ‘brut’ bubbly is maybe 5% of the calorie content.

Not everything has to be about health.

From the New York Daily News: Study finds gin and tonic drinkers are more likely to be psychopaths, sadists

That’s not quite what the study finds. A slightly revised version is a couple of paragraphs into the story (credit for linking, but with a penalty for not mentioning it’s from 2015)

Researchers at Innsbruck University found that people who enjoy bitter flavors like the tonic water in a gin and tonic, black coffee, and dark chocolate are more prone to “Machiavellianism, psychoticism, and narcissism,” among other traits.

Here’s the list of ‘bitter’ flavoured foods they used (from)

Q: Did you see that drinking Champagne every day can prevent dementia?

A: Didn’t that story come out a while ago?

Q: June, I think. But it’s more relevant now. And it’s going to be 38C today, so it’s not like you have anything better to do. And Champagne is seasonal at the moment.

A: Ok, ok.  I’ll look it up

A: Here’s the press release

Q: That’s dated 2013. Are you sure it’s the right one?

A: It was linked from one of the stories you gave me.

Q: And you found the research paper?

A: Yes. That’s also from 2013

Q: It’s in a journal called Antioxidants and Redox Signalling? That doesn’t really sound like a medical journal about dementia.

A: No, it doesn’t.

Q: How many people were in the study?

A: None

Q: Ok, how many mice?

A: 8 elderly rats in each of three treatment groups: control, alcohol, Champagne.

Q: And the Champagne rats were less likely to get dementia?

A: No, they did slightly better on tests involving remembering whether they’d found a food pellet in the left or right tunnel of a maze.

Q: How long were they given Champagne diet?

A: Six weeks.

Q: But it was real Champagne

A: Yes — the researchers think that because Champagne is made partly with red-wine grapes such as Pinot Noir it will contain beneficial compounds similar to those in red wine

Q: But doesn’t red wine also contain compounds similar to those in red wine?

A: Indeed. You could just drink the Pinot Noir straight.

Q: Three glasses a day seems quite a lot, especially for a rat.

A: That’s scaled by body weight: 1.78 ml/kg

Q: And do rat doses usually scale that way to humans?

A: No, if you use a more standard formula you end up with about 1.3 glasses per week as the equivalent dose in people.

Q: Not such a good headline

A: No

Q: We’d know if 1-2 glasses of red wine per week prevented dementia, wouldn’t we?

A: Yes, probably. The usual message applies: if you’re drinking champagne primarily for the health benefits, you’re doing it wrong.

The University is closed until after the New Year, so this is the StatsChat silly season.

To start with, a quiz question:

What is unusual and StatsChat-relevant about this molecule?

From the New York Times, in what’s otherwise a really interesting story

The prospectors had unearthed what would come to be called the Patricia Emerald: a dazzling 12-sided crystal roughly the size of a soup can, with a weight of 632 carats — more than a quarter of a pound

If you have a rock `roughly the size of a soup can’ it’s going to weigh more than a soup can roughly the size of a soup can. A standard US can of soup has volume 10 fluid oz, and weighs over half a pound.  The Patricia Emerald is more the size of one of those small coconut cream cans — which, to be fair, is seriously impressive for an emerald.