Stats Chat

I linked earlier to Jeff Leek’s post on fivethirtyeight.com, because I thought it talked sensibly about assessing health news stories, and how to find and read the actual research sources.

While on the bus, I had a Twitter conversation with Hilda Bastian, who had read the piece (not through StatsChat) and was Not Happy. On rereading, I think her points were good ones, so I’m going to try to explain what I like and don’t like about the piece. In the end, I think she and I had opposite initial reactions to the piece from on the same starting point, the importance of separating what you believe in advance from what the data tell you. (more…)

• Nate Silver’s fivethirtyeight.com is live. He writes about data journalism and what it is
• Also at 538, Jeff Leek (from Simply Statistics) Finally, a Formula For Decoding Health News

• At Pantheon, a visualisation of globally known people over time

• Genetics can shed a lot of light on disease, but not always. Derek Lowe writes about a new study of bipolar disorder, where the genetic associations seem amazingly diverse and inconsistent.

[Update: Just had to add this one from a Huffington Post survey: Nearly a quarter of Americans know what we should do about the Ukraine Administrative Adjustment Act of 2005]

If you have time, there’s an interesting event that will be streamed from New York University this (NZ) morning (10:30am today NZ time, 5:30pm yesterday NY time)

..the Data & Society Research Institute, the White House Office of Science and Technology Policy, and New York University’s Information Law Institute will be co-hosting a public event entitled The Social, Cultural, & Ethical Dimensions of “Big Data.” The purpose of this event is to convene key stakeholders and thought leaders from across academia, government, industry, and civil society to examine the social, cultural, and ethical implications of “big data,” with an eye to both the challenges and opportunities presented by the phenomenon.

The event is being organised by danah boyd, who we’ve mentioned a few times and whose new book I plan to write about soon.

The latest BNZ-REINZ Residential Market Survey is out, and the Herald has even embedded the full document in their online story, which is a very promising change.

According to the report 6.4% of homes sales in March are  to off-shore buyers, 25% of whom were Chinese. 25% of 6.4% is 1.6%.

If you look at real estate statistics (eg, here) for last month you find 6125 residential sales through agents across NZ. 25% of 6.4% of 6125 is 98. That’s not a very big number.  For context, in the most recent month available, about 1500 new dwellings were consented.

You also find, looking at the real estate statistics, that last month was February, not March.  The  BNZ-REINZ Residential Market Survey is not an actual measurement, the estimates are averages of round numbers based on the opinion of real-estate agents across the country.  Even if we assume the agents know which buyers are offshore investors as opposed to recent or near-future immigrants (they estimate 41% of the foreign buyers will move here), it’s pretty rough data. To make it worse, the question on this topic just changed, so trends are even harder to establish.

That’s probably why the report said in the front-page summary “one would struggle, statistically-speaking, to conclude there is a lift or decline in foreign buying of NZ houses.”

The Herald  boldly took up that struggle.

The cosmologists are excited today, and there is data visualisation all over my Twitter feed

RT @Resonaances: Parameter space of inflation as of today: pic.twitter.com/i45NLQX9DI Honestly didn’t think I was going to see > 0 for a while!

— Renee Hlozek (@reneehlozek) March 17, 2014

That’s a nice display of uncertainty at different levels of evidence, before (red) and after (blue) adding new data.  To get some idea of what is greater than zero and why they care, read the post by our upstairs neighbour Richard Easther (head of the Physics department)

Each week, we would like to invite readers of Stats Chat to submit nominations for our Stat of the Week competition and be in with the chance to win an iTunes voucher.

Here’s how it works:

• Anyone may add a comment on this post to nominate their Stat of the Week candidate before midday Friday March 21 2014.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of March 15 – 21 2014 inclusive.
• Quote the statistic, when and where it was published and tell us why it should be our Stat of the Week.

Next Monday at midday we’ll announce the winner of this week’s Stat of the Week competition, and start a new one.

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Q: Did you see the story about aphrodisiacs on Stuff this weekend?

A: Yes

Q: How did they find out which ones worked?

A: It says “Richard Cornish investigates the only way he knows how.”

Q: Randomised n-of-1 trials with independent evaluation by someone who doesn’t know what he’s eaten?

A: Sadly, no.

Q: Allocating different foods, and some control foods, to a large group of people and collecting their reports?

A: No

Q: Getting a librarian to help him review the scientific research on the topic? Or the traditional knowledge?

A: Not really, though there are some biochemical or historical anecdotes for many of the items.

Q: Um. Did he just try each food as you would if you wanted to use it as an aphrodisiac?

A: Not that, either.

Q: I give up. What did he do?

A: ” It was my task to consume them in a bland environment, with no chance of any stimulation or excitement.”

Q: What a waste. But aren’t you being a bit harsh?  He’s a food writer and TV producer. He does sustainability and Spanish food. He’s not a science journalist or an investigative reporter.  They didn’t expect anyone to take it seriously.

A: Ok, but some of the nutrition stories and sex stories they run are supposed to be taken seriously. It should be easier to tell which is which online.

Q: Wait, isn’t it March now?

A: Yes.

Q: That sounds more like a Valentine’s Day column

A: An interesting point. You thought of that faster than I did.

Q: Well?

A: It is a Valentine’s Day column. From the Southland Times. Except they took out the foie gras and truffles to make it suitable for the national audience. Reruns aren’t just for The Simpsons, you know.

• Your high school transcript will haunt you forever? Partly reasonable, but partly the recurring claim that knowing what works in a given situation will take away your freedom.

• Both men and women think women are bad at math. “Men and women employers alike revealed their prejudice against women for a perceived lack of mathematical ability. When the only information that the employers had was a photograph of the candidate, men were twice as likely to be hired for the simple math job, no matter whether it was a man or woman doing the hiring”. Could do with a lot more scare quotes around words like `employer’, `candidate’, `hired’, but a good report.

• Why Google Trends can’t track the flu (yet) There are lots of differences between flu season and the rest of the year, and the ones most relevant to Google’s ordinary activities don’t have much to do with influenza

The Herald said, on Friday “Fewer workers stoned on the job”

Information from the New Zealand Drug Detection Agency showed 81,410 on-site drug-screening tests were carried out last year, 16 per cent up from the previous year.

But only 5.5 per cent of tests showed the presence of drugs, down from 6.4 per cent in 2013

As usual, there’s no mention of the fact that NZDDA is just one of the private companies offering drug testing services. It took me a long time to realise this, until I was tipped off by a news story advertising one of their competitors.

Presumably NZDDA don’t think their customers choose them at random, and with no real reason for wanting testing. If customers were behaving even a little rationally you’d expect an expansion of drug testing to pull in lower-risk employees. If we look at the actual number of positive tests, using the quoted figures, it was about 4480 last year and about 4490 in the previous year. Given no change in the number of positive tests and a 1 percentage point change in the proportion of positive tests, from a single company, there’s not a lot of numerical evidence for an increase in number of workers with detectable cannabis in their systems.

More importantly, there’s no evidence whatsoever for the ‘stoned on the job’ headline: absolutely no information is given about this. One of the big problems with cannabis testing is that there is no useful biochemical assay for being stoned. Detectable levels persist long after impairment is over, and even when you’re actually stoned there is not a good relationship between drug concentration and impairment.  This is a real problem for Washington and Colorado, which have legalised cannabis and need to set driving laws. In contrast to alcohol, if you actually care about safe driving and cannabis, it’s really hard to get a useful and objective test.

The story ends with two examples of disasters. In one, cannabis was definitely ruled out as a contributing factor; in the other, the conclusion was only that “it could not be excluded”. The NZDDA  press release is at Scoop, and despite how the story reads, there is surprisingly little text in common.

The Sunlight Foundation has released its internal data visualisation style guidelines (via)

Some of it is just one organisation’s house style, but it’s an attractive style. Some of it is generally useful advice. The main thing they are missing is any advice on representing uncertainty.