Posts filed under General (844)

February 8, 2016

Nice cup of tea

Q: So, did you see that tea prevents hip fractures now?

A: The Herald story? Yes.

Q: Is this mice?

A: No, people.

Q: But it’s not experimental, it’s just correlation?

A: Yes, but better than usual.

Q: Why?

A: The two big problems with diet studies are that measurements are horribly inaccurate and that people who have healthy diets are also weird in lots of other ways which it’s hard to disentangle.

Q: So tea is different because it’s easy to measure?

A: They divided women into “3+ cups per day”, “Basically never”, and a middle group.  It’s not hard to distinguish people who drink tea as their main liquid intake from people who hardly ever drink it.

Q: And the healthy weirdo effect?

A: Tea drinking isn’t really thought of as a health thing, and (among 80 year old Australian women) it’s probably not a social class marker either.

Q: You usually complain about extrapolation as well. Did they really measure bone density?

A: Better than that, they really measured hip fractures.

Q: So we can believe it?

A: Perhaps?

Q: What’s your issue with this one, then?

A: The evidence isn’t overwhelmingly strong, and we wouldn’t have heard about this study through the media it if it wasn’t positive. And there have been a lot of other studies with mixed results.

Q: As good as this one?

A: No, but still.

Q: Would it have helped if they’d measured bone density?

A: They did, and they found it didn’t explain all the correlation with tea drinking, which is a bit surprising.

Q: Don’t you always tell people those mediation analyses are unreliable?

A: I suppose. But bone mineral density is measured pretty accurately, so it should work better than usual.

Q: Why don’t you want tea to be beneficial?

A: I do want tea to be beneficial; I drink a lot of it. But almost nothing prevents hip fractures, and this is a big difference.

Q: How big?

A: More than 40% reduction for hip fractures, which is in the ballpark of what the potent bisphosphonate drugs manage.

Q: So should we drink tea?

A: It’s unlikely to be harmful, and it might help with fractures. If you hate the taste, though, this probably isn’t strong enough evidence to force yourself to drink it.

Q: How about eating green tea KitKat?

A: I’m fairly sure consumption of that was low in this cohort of elderly Australian women.

February 7, 2016

Why do we care?

From the history of the Manchester Statistical Society

Manchester Statistical Society was a pioneering organisation: It was the first organisation in Britain to study social problems systematically and to collect statistics for social purposes. In 1834 it was the first organisation to carry out a house-to-house social survey.

The Society was formed in September 1833 at a time of severe social problems. Few of the founders were statisticians in the modern, technical sense. But, they were interested in improving the state of the people and believed that establishing the facts regarding social problems was a necessary first step. 

From an earlier organisation in London (via)

‘The privation and misery endured by the productive classes of society in Great Britain in 1816 and 1817, led to the formation of an Association in London, for the purpose of investigating the nature and extent of that misery; and of ascertaining, if possible, how far it resulted from avoidable or from unavoidable causes; and how far repetitions of similar ills were likely or not to occur’.

Groups of wealthy men saying they want to improve society isn’t new.  Nor is it new that they don’t know enough to do much good.  What was different in the early nineteenth century was that they recognised they didn’t know enough. The Statistical Societies were founded to provide information about social problems that went beyond any individual’s range of anecdotes, because the truth mattered.

The range of statistics has broadened immensely since then, especially with the help of computers. At the foundation is still the principle that one person’s reckons aren’t enough: the world is more complicated than that and the truth matters.

I’m not arguing that statistics has to be Important and Serious. If you want to know whether The Rock plays the same music at the same time each day or who is likely to win the rugby, statistics can help there. If you care enough about how other people eat their cereal, that’s a valid topic for investigation. The bottom line is that you do actually care about the answer; that the truth matters.

For a depressingly large fraction of surveys in the news today, no-one really cares whether the answer is accurate or even what the question means. Maybe it’s ok to have sections of the newspaper where facts aren’t really relevant — you need to ask a journalist, not me. But when the truth doesn’t matter, stop pretending to use statistics.


  • Locksmiths gaming Google and Google Maps: from the New York Times. 
  • We have “lead generation systems” here too, but I haven’t seen any suggestion that these are scams, just somewhat misleading advertising aiming to look local. Eg, from a site that’s appealingly honest about how it works

If your business covers the whole of Auckland for example then we would set up 200 websites for you which is one for every suburb in the city covering 6 districts

  • What’s the first word that comes to your mind starting with SUPP? If you said “SURGERY”, you’re not alone — or maybe you’re not real. “Disturbing oddities” in a research paper.
  • A map of the longest flights — Auckland-Houston and Auckland-Vancouver don’t make it.
  • Herald Insights has an exploration of unemployment rates over the recession and recovery, by census ethnic group and age.
  • A company that may be taking measurement too far: “Any meeting of at least three people is expected to hold at least one poll.”
February 6, 2016

Bogus polls from Nature

Soon after Twitter polls were introduced, Al-Jazeera News used one to poll its followers about US intervention in Syria. Fortunately, it seems to have been a failed experiment (the poll, that is).

Now, Nature News is doing it:


Twitter polls can work as jokes and commentary, and they might work for gathering opinions from your friends. They shouldn’t be allowed to masquerade as data collection.

February 5, 2016

DIY investigations

So, the Herald has a story headlined Men’s DIY skills ‘dying out’ – study. Here’s the first three paragraphs

Men are no longer able to carry out traditional DIY – with most now opting to call in tradesmen, research shows.

Most men cannot change a tyre, while only half can wire a plug and just one in five are able to fix a dripping tap.

Three in five men would need to call in a plumber to unblock a toilet, while only a third feel confident about putting together flat-pack furniture.

You might think this raises some questions. For example:

  • Is there any information in the story suggesting the numbers are reliable? (not really)
  • Do they have comparable data from the past to support the ‘dying out’, ‘no longer able’ and so on? (no)
  • Isn’t this whole gendered housework thing mildly offensive and about five decades out of date? (yes)
  • Hasn’t it been a cliche since flat-pack furniture was invented that most people don’t feel confident assembling it? (yes)

A question that might not spring immediately to mind: “What country are these numbers from?”

The stock photo isn’t much use. It shows a man carrying a plank while smiling — maybe one of the other dying skills?  Google Image Search finds a vendor who has it tagged as Calgary, Alberta (Canada).

However, there are two clues in the text I’ve quoted.  The first clue is that there aren’t any specifically NZ journalistic cliches — it’s hard to imagine a Kiwi writing this sort of crap without referencing, say, number 8 wire.

The second clue is more subtle: “only half can wire a plug”.  Until 1992, appliances in the UK were often sold without plugs attached, and wiring a plug was a more important household skill than in the rest of the world.

Reading on, the fourth paragraph confirms that this is a UK story. It’s from the Daily Mail and it exists to advertise a UK men’s clothing company.  If you found the story annoying, I would encourage you not to investigate their blog further.

A modest proposal: it appears that news sites have to publish a certain number of these surveys. Maybe they could trim out the name of the sponsoring company, and just provide it in a link for readers who really cared? Then the story could be assessed on its true news (or perhaps entertainment) value.


Returning-from-travel edition

  • Wordbank is an open database of information about children’s vocabulary growth. With pointy-clicky apps.
  • The Ethical Data Scientist. Cathy O’Neil, writing at Slate. “As long as our world is not perfect, and as long as data is being collected on that world, we will not be building models that are improvements on our past unless we specifically set out to do so.”
  • Billboards that use DNA on discarded cigarette butts or gum to recreate images of the litterer. “Obviously we have no photos of the original litterers to compare the sketches to, but according to Oglivy, the results are accurate.” [trust us, we’re an advertising agency]
  • HeadlineRevealed: The drug that keeps you young. Story: “Experts say they had extended the lifespan of mice by 35 per cent” and “The one used on mice is not suitable for people”
February 3, 2016

Units matter

I think this is just a typo in the Herald story about testing for methamphetamine in state houses:

Forensic scientist Dr Nick Powell said any meth contamination above 0.5mcg per 100sq m of surface risked headaches, coughs and sleeplessness, and poorer appetite and infant brain growth.

The NZ standard for cleanups is 0.5μg per 100cm2, which is designed to be safe, rather than just on the borderline of danger, so even with square centimetres this is a strong claim. Changing the denominator to square metres makes the claim ten thousand times stronger.

February 2, 2016

Not everything is a breakthrough. But.

Jack Scanlan, at Lateral

Steps could be taken to reduce the hype associated with every tiny step towards curing a disease or developing a new technology, but the trade-off would be a reduction in the amount of science making its way to the public.

Helpful prediction vs recycled prejudice

From What World Are We Building?  by danah boyd

One of the perennial problems with the statistical and machine learning techniques that underpin “big data” analytics is that they rely on data entered as input. When the data you input is biased, what you get out is just as biased. These systems learn the biases in our society, and they spit them back out at us.


January 27, 2016

Meet Statistics summer scholar Xiangjie Xue

XiangjieEvery summer, the Department of Statistics offers scholarships to a number of students so they can work with staff on real-world projects. Xiangjie, right, is working on vector generalized linear and additive models (VGAM) for R with Dr Thomas Lee. Xiangjie explains:

“I am trying to help Dr Yee to improve the functionality of the VGAM package. This includes writing some functions from scratch, improving the efficiency of the existing functions and testing functions. To do this, I will need to learn the underlying structure of R and write or translate some functions from other computing languages to C or R.

“I came to the University of Auckland to do my undergraduate Applied Mathematics and Operations Research in 2012.

“After I finished, I received offers to do both Applied Mathematics and Statistics. When I was trying to decide the topic of my Honours project, I realised that Statistics covers a very broad range of topics and that they are very closely related to each other – I could learn data analysis, computing or probability theory and stochastic processes. All of these topics are really useful in our daily lives. I was really fascinated by this, so I decided to study Statistics instead of Applied Mathematics. I am thinking about pursuing a masters degree or a PhD in Statistics this year.

“This summer, I am hoping to travel more in New Zealand. In fact I went camping recently with my high-school friends in Whangarei and the Bay of Islands region and I had a great time. Besides travelling, I’d like to spend some time relaxing at home, watching my favourite shows.”