Posts from March 2014 (59)

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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If you’d like to comment on or debate any of this week’s Stat of the Week nominations, please do so below!

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.

• Ok, it’s not statistics as such, but you have to see the mash-up of the Cyclone Lusi animation and Van Gogh’s Starry Night, by @bobsyouruncle

• Cathy at Mathbabe.org on survey questions, pointing out that the sun does too go around the earth.

• Buzzfeed says “According To Pornhub, The South Watches More Gay Porn Than Any Other Part Of The U.S.” The point, for those of you not up on US sociogeography, is that the South is religiously conservative.  It turns out that’s not really what the data say. The figures aren’t % of men who watch gay porn, they are % of porn that is gay male. The data are equally consistent with straight guys in religiously conservative states watching very slightly less porn than those in other states. Data on total porn consumption are mixed.

• ProPublica, the non-profit, public-interest journalism foundation in the US, are setting up a data shop. Data that they could just download, they’ll make available for free, but the data that took a lot of effort will cost. Interesting to see this as a data journalism funding model.

• From ProPublica, a good example of simple arithmetic applied to unreasonable claims.

Since 2009, Dagogo-Jack has been paid at least $257,000 by Glaxo, Lilly and Merck.

“If you actually prorate that by the hours put in, it is barely more than minimum wage,” he said. (A person earning the federal minimum wage of $7.25 would have to work 24 hours a day, seven days a week for more than four years to earn Dagogo-Jack’s fees.)

Cyclone Lusi, from the earth wind animation

And coloured by total precipitable water (orange: dry, light blue: very wet)

Keep safe.

The basic method is described on my Department home page. I have made some changes to the methodology this year, including shrinking the ratings between seasons.

This week I don’t have full details because I have limited internet access and am having to copy the details from my computer.
 

Predictions for Round 2

Here are the predictions for Round 2. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 5

The basic method is described on my Department home page. I have made some changes to the methodology this year, including shrinking the ratings between seasons.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 22 matches played, 14 of which were correctly predicted, a success rate of 63.6%.

Here are the predictions for last week’s games.

Predictions for Round 5

Here are the predictions for Round 5. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.