Posts filed under General (801)

November 27, 2015

To find the mind’s construction near the face

Q: This Herald photo caption says “Men with facial hair showed much higher levels of hostile sexism, the study found.”  Did it?

A: No.

Q: Ok, how about the introduction “Bearded men will just have to take it on the chin – they are, apparently, more sexist.”?

A: Not really.

Q:  <sigh> Was this mice again?

A: No, there aren’t good animal models for these variables, as far as I know.  It was people.

Q: University students?

A: No, that’s so five years ago. It was a survey on Amazon’s Mechanical Turk, of men from the US and India.

Q: A representative survey?

A: Well, they paid people US$0.25 to participate, so I’m guessing maybe not. It’s probably better than using an undergraduate psychology class, though.

Q: And they measured sexism and beards over the internet?

A: The sexism was a standard questionnaire, so I think we should accept it. The participants were shown a set of facial hair images and asked to pick what their facial hair looked like. Probably ok, too.

Q: And men with beards were the most sexist?

A: No, men with moustaches, goatees, or soul patches.

Q: Then men with beards?

A: Then ‘light beards’, then light and heavy stubble, then heavy beards, then clean-shaven, then light medium beards.

Q: So it’s not primarily beards, it’s more other sorts of facial hair?

A: That’s what the study suggests

Q: Just like the photo caption?

A: Up to a point. “Much higher” is pushing it.

Q: How much higher?

A: About a third of a point, on a six point scale. About 1.5% of the variation between men could be predicted by their facial hair.

Q: Is there a bar chart, perhaps cut off at some non-zero value?

A: You’ve been reading the Daily Mail, haven’t you? Yes, there is:


Q: That’s not a very big difference, is it?

A: No

Q: So some men with facial hair are probably ok?

A: Probably.


November 25, 2015

What do statisticians do all day?

The New Zealand Statistical Association is having its annual meeting at the moment in Christchurch. It’s hard for a lot of people to imagine how there could be new research in statistics, so here are some examples from the awards.

Maxine Pfannkuch won the Association’s lifetime achievement award, for her work on statistics education. She studies how people (mostly schoolkids) draw informal statistical conclusions from data and from graphics, and looks for ways to teach them to do it better. A lot of the improvements in the high-school stats curriculum are her fault.

Mark Holmes won the research award. His research is harder to explain in simple terms, but he studies random processes that accumulate over time — like the shape of the trail left by a randomly-moving point.

Blair Robertson won the junior research award. He used to be an applied mathematician, working on optimisation — finding the best value of a complicated function. He now uses similar techniques to come up with improved ways to choose sets of locations in space and time for environmental sampling.

Maarten Kruijver won a `young statistician’ talk award. He works in forensic statistics, looking at ways to estimate the chance that a DNA sample from a crime scene will coincidentally look as if it is from a close relative of someone in the police database.

Anjali Gupta won the other `young statistician’ talk award. She is studying a laser-based technique for measuring chemical composition of things, with forensics being one application.  She was studying the variation in measurements for the same object over time, to understand more about the accuracy of the technique.

November 24, 2015

Book recommendations

It’s the time of year when people are asking “What can I buy for my favourite nerd?”. Here are some books s/he might like, a mixture of older and new.

  • Thing Explainer by Randall Munroe (of XKCD fame). A coffee-table book of annotated drawings, along the lines of his 2012 Up Goer Five. I reviewed this for the Listener.  It’s really good.
  • Eureka: Discovering Your Inner Scientist by Chad Orzel.  I’ve mentioned this book before on StatsChat. It’s a great look at how science works. In the process, it attacks a lot of the myths about scientists.
  • Thinking, Fast and Slow by Daniel Kahneman. With Amos Tversky, he pioneered the study of why people are bad at probability and risk assessments. He won a Nobel-like Prize for Economics shortly after the book came out. Unlike many books of its kind, it doesn’t need the subtitle “Why I am Right About Everything”.
  • The Immortal Life of Henrietta Lacks, by Rebecca Skloot. The HeLa cell line is a mainstay of laboratory research, but until fairly recently even most scientists didn’t know where it came from. Skloot’s book tells the story of an African-American woman treated for cervical cancer at Johns Hopkins, and how her cells lived on without her or her family’s knowledge.
  • How Not To Be Wrong by Jordan Ellenberg. Ellenberg is a highly-respected pure mathematician, but his book is about statistical thinking in everyday life.
  • The Canon, by Natalie Angier. A survey of the most important things we’ve learned about the universe. Includes a chapter on probability and statistics featuring the wonderful Deb Nolan.
  • The Secret Life of Money, by Daniel Davies and Tess Read. One of the many books trying to explain the world in terms of microeconomics or vice versa. Less everything-you-know-is-wrong and more entertaining writing than Freakonomics.  I’m not sure if reading Davies’s account of a visit to New Zealand will make you more or less likely to want the book.
  • The Philadephia Chromosome, by Jessica Wapner. This tells the story of the selective tyrosine kinase inhibitor imitanib (Gleevec),  and its (largely unfulfilled) promise of cancer treatment targeting the cause of disease without toxic side-effects.
  • The Disappearing Spoon, by Sam Kean. The eponymous spoon is made of gallium, which melts at about 30C; the book is an entertaining and informative survey of the periodic table.
November 22, 2015


  • There’s a survey put out by the World Bank with what it calls basic financial literacy questions. Lots of people didn’t give the intended answers.  As Felix Salmon explains, that’s because they were silly questions:

Nothing useful can be learned by going up to poor workers in, say, Afghanistan (to take the very first country on the list), and asking them this question. They don’t have banks, and if they do have banks they don’t have savings accounts, and if they do have savings accounts they don’t hold on to them for five years, and if they do hold on to them for five years they’ll probably end up with nothing at all…

  • From Andrew Gelman’s blog, a couple of posts on accidental and deliberate wrong answers in surveys.
  • Graeme Edgeler explains again why you don’t need deliberate wrong answers in the flag referendum
  • Some things shouldn’t be maps. One example is homes of 187 victims of child homicide over the past 23 years, mapped with the 2013 deprivation index in Stuff.  On top of the inappropriateness of the map, and the time misalignment, there does actually exist serious research on risk factors for child abuse, both here and abroad: it’s not a matter of Stuff ‘discovering’ things.
  • David Spiegelhalter on an example of misreporting of criticism of misreporting of stats
  • US artist Chad Hagen has a lovely set of prints titled “Nonsensical Infographics“, with the form of data visualisation but no content3626_largeview_cbca1479-548b-467f-9997-e25d0ff76662_large


November 19, 2015

False positives

I searched for “Joe Hill” on Google a few months ago, and the “aren’t we clever” box popped up with:


The statistics and  computation behind these searches is impressive: in addition to all the usual Google stuff, the system realises that the – fairly common – words “joe” and “hill” occur together sufficiently often that they are probably a thing. Then it takes advantage of Wikipedia to realise that “joe hill” is the name of a person, not a geographical feature or a coffee shop (or, I suppose, profanity), and finds pictures and information. And it almost works — even with people who aren’t especially well known.

The gentleman on the left really is Joe Hill (author), aka Joseph Hillstrom King. One of his books has been made into a movie starring Daniel Radcliffe, so he’s definitely successful but not in any sense a mainstream celebrity. The gentleman on the right is someone else. People with an interest in labour history or folk music will recognise Joe Hill (activist), aka Joseph Hillstrom ,aka Joel Emmanuel Hägglund: I dreamed I saw Joe Hill last night, alive as you and me”. It’s an understandable mistake for the Google: the modern Joe Hill was named after the historical one, and there will be a lot of cross-referencing of the two. And it doesn’t really matter.

Joe Hill (activist) was involved in a rather more important false positive. The song says “they framed you on a murder charge”, and it’s only exaggerating a bit. There was strong circumstantial evidence and Hill refused to give any explanations, but it also appears the eyewitness testimony was manufactured. He was executed 100 years ago today.

November 13, 2015

Drug subsidy arithmetic

There are new, very promising treatments for some cancers, which work by disabling one of the safety mechanisms in the immune system so that it can attack the tumour. These treatments have been approved in the US for melanoma and the most common type of lung cancer, and they look better than anything we’ve seen before.  The problem is the price, more than NZ$200,000.

In New Zealand, roughly 2000 people die of melanoma or lung cancer each year. At the current market prices, a course of treatment for each of them would absorb more than half of Pharmac’s budget.

It’s not even as if the $200,000 guarantees a cure. The results of the KEYNOTE trial in melanoma were impressively good by the standard of melanoma treatment, but:

The overall response rate was 34% and the complete response rate was 6%. Eighty percent of responses were still ongoing at the time of analysis, and the median duration of response has not yet been reached.

There really are people whose disease completely vanished, but only about one in sixteen. Two thirds didn’t see any response. Even for the people who have no detectable disease we can’t yet know if the benefits will last a few years or a lifetime.

Pharmac is not going to fund these treatments at anything like the current price in the current budget. That’s not a matter of debate or public pressure. It’s just not happening. It won’t add up. Conceivably, the government could decide to come up with the money to fund the treatments outside the current Pharmac budget. I don’t think that would be the best way to spend the money, but I’m glad to say this is the sort of decision I don’t get to make.

Over the next few years, other companies will introduce treatments that attack the same or related immune checkpoint targets, and competition will make the price fall. At some point, it will be worthwhile for drug companies to make Pharmac an offer it can accept, as happened recently with Humira, Pharmac’s current top spend (which turns off the immune response in a somewhat similar way to how the new cancer treatments turn it on).

Five years ago, you couldn’t get these treatments if you were a billionaire. In ten years or so, I expect these or similar treatments will be effectively free to New Zealanders. At the moment, we’re in the painful transition period, where the manufacturers can afford to target only the wealthiest individuals and insurance companies.

November 10, 2015


  • One of the problems with reducing things to hypothesis testing is that you often don’t want to make a one-off decision. A comic from Saturday Morning Breakfast Cereal makes this point, but in a case where you really do want to make a one-off decision.
  • From StuffMost women are either lesbian or bisexual’ but never straight, study claims”. From the Daily Beast: “Um, yes, straight women are real”
  • Digit preference in US football “The only explanation that has stuck with me is that when a official thinks ‘oh damn this is a mess, there are seven separate six foot tall millionaires all piled up on top of the ball and I have 100 rules to try and remember, where did that ball stop?’  their subconscious makes them grab for the safety blanket of a line drawn and place it down on there.”
  • Digit preference in marathons: People really prefer to run 3:59 rather than 4:00 (early last year, from some economists at Chicago(PDF), but you probably saw the New York Times version)
  • A useful bit of arithmetic for “Why isn’t this medication free?” stories. Pharmac’s budget is a little under $800 million per year.  There are about 4.5 million people in New Zealand, so that’s under $200 per person per year, or under $16,000 per person per expected lifetime. Based on more accurate inputs, it’s about $14,000 per person per lifetime.
  • In the US, mortality isn’t falling for 45-54 year olds identifying as white the way it is for basically everyone else in the West. If you read lots of statistics blogs, you will have seen discussion about whether mortality in this group is really rising or not: the peak of the baby boom just swept through the 45-54 band, so the average age of people in this group has increased. That’s worth looking at, but doesn’t change the basic message.
November 9, 2015

NZ Herald promotes data

Today (assuming nothing went wrong overnight) the Herald is giving data journalism a much higher profile: Insights

Harkanwal Singh and Caleb Tutty have been working frantically to assemble and format the past data visualisations and do new stuff for the launch. You should check it out: the way to convince the Herald management that good local data journalism is more valuable than bogus UK health stories is for it to get pageviews.

November 3, 2015


  • Cancer cure hype: In a five-day period in June, 36 cancer drugs were described in the news as “breakthrough”, “game-changer”, “miracle” or similar words. Five of them had not yet been tested in humans.
  • Similarly , from Vox, on a 2003 study: “They looked at 101 studies published in top scientific journals between 1979 and 1983 that claimed a new therapy or medical technology was very promising. Only five, they found out, made it to market within a decade.” Most promising treatments don’t work: that’s not cynicism, it’s empirical fact. Of course, it’s only with new pharmaceuticals that we find out they don’t work.
  • An XKCD comic on Bill Gates’ blog, talking about the importance of being boring and non-innovative to finally finish off polio
  • London has a smaller proportion of residents born overseas (37%) than Auckland (39%). So does New York (37%). No real conclusion, just that it’s interesting. (via Hayden Glass)
  • “Cartography — what maps reveal about ourselves” from the BBC
  • Typically beautiful use of interactive graphics and maps in a New York Times story about ice melting in Greenland.
November 2, 2015

Have you ever tasted tofu?

Q: Did you see that an Asian diet helps ward off the effect of menopause?

A: An “Asian diet?” Do they mean Afghan, Punjabi, Bengali, Goan, Kirghiz, Uighur, Malaysian, Thai, Vietnamese, Lao, Korean, Beijing, Sichuan, Shanghai, …

Q: Ok, yes, I get the point.  Did you see that a diet with lots of soy, similar to Japanese and some Chinese diets, helps prevent fractures and heart attacks?

A: The story about phytoestrogens? Yes.

Q: And do they?

A: Hard to tell.

Q: Was it mice again?

A: No, this was a proper randomised trial in women. It’s just they didn’t measure fractures or even bone density.

Q: What did they measure?

A: The concentration of two proteins that are involved in bone formation

Q: How reliable is that?

A: By the standards of purely biochemical laboratory markers, not bad. An article in the newsletter of the American Association for Clinical Chemistry said “Commercially available immunoassays for all the markers are reasonably bone-specific and reflect bone turnover in postmenopausal osteoporosis and following anti-resorptive therapy.

Q: I can sense a ‘but’ coming on here

A: The story doesn’t say how big the changes were, and since this is only a forthcoming conference presentation, it’s hard to find out much detail. The abstract is here.

Q: How does it work?

A: Soy beans contain chemicals that weakly stimulate oestrogen receptors and so have some of the effects of oestrogen.

Q: Oh, like the dangerous endocrine disrupting pollutants I keep hearing about?

A: No, those are synthetic chemicals, not natural dietary components.

Q: That’s a remarkably good poker face you have

A: Can we move on?

Q: Ok, so what about the cardiovascular risk factors? The story says “They were also less at risk of heart disease, which oestrogen is also thought to protect against.” Did they measure heart disease?

A: No, they measured “cardiovascular risk markers”

Q: Does oestrogen improve these “risk markers”?

A: Yes, it does.

Q: Wait, wasn’t there a big trial of oestrogen and heart disease risk?

A: You mean the Women’s Health Initiative? Yes, there was.

Q: Did they see these improved risk markers?

A: Yes

Q: And a reduction in fractures?

A: Yes.

Q: But they didn’t see a reduction in heart disease, did they?

A: No, an increase. Over all, serious chronic disease was very slightly worse with oestrogen supplements.

Q: So why do we expect soy to be different?

A: An excellent question