Posts from August 2012 (64)

From the Otago Daily Times:

Over the weekend, police dealt with seven separate incidents involving Australians, including theft, nudity, disorderly behaviour and gross intoxication.

Sergeant Mark Gill said although the numbers appeared to show the Australians behaving badly, it was proportional to Queenstown’s Australian visitor ratio with other nationalities.

The common denominator in many small crimes in Queenstown’s CBD was too much alcohol and that was an issue for the police, Sgt Gill said.

Looking at the rest of his comments, Sgt Gill is clearly trying to stop Queenstown looking dangerous and scaring off tourists, but it’s encouraging whenever we see denominators being used sensibly in public by people who aren’t (as far as I know) trained professionals.

The aphorism that adorns StatsChat is actually a paraphrase, by the statistician Samuel Wilks in a 1951 speech, of what H.G. Wells wrote.  The full paragraph from Wells’  Mankind in the Making (1904) is

Modern, too, is the development of efficient mathematical teaching; so modern that for too many schools it is still a thing of tomorrow. The arithmetic (without Arabic numerals, be it remembered) and the geometry of the mediaeval quadrivium were astonishingly clumsy and ineffectual instruments in comparison with the apparatus of modern mathematical method. And while the mathematical subjects of the quadrivium were taught as science and for their own sakes, the new mathematics is a sort of supplement to language, affording a means of thought about form and quantity and a means of expression, more exact, compact, and ready than ordinary language. The great body of physical science, a great deal of the essential fact of financial science, and endless social and political problems are only accessible and only thinkable to those who have had a sound training in mathematical analysis, and the time may not be very remote when it will be understood that for complete initiation as an efficient citizen of one of the new great complex world-wide states that are now developing, it is as necessary to be able to compute, to think in averages and maxima and minima, as it is now to be able to read and write. This development of mathematical teaching is only another aspect of the necessity that is bringing the teaching of drawing into schools, the necessity that is so widely, if not always very intelligently perceived, of clearheadedness about quantity, relative quantity, and form, that our highly mechanical, widely extended, and still rapidly extending environments involve.

In 1904, it was reasonable to describe the analytic techniques needed to make `endless social and political problems’ accessible and to achieve `clearheadedness about quantity, relative quantity, and form’ as “mathematics”.  Today we would usually call these “statistics”, although “numeracy”, or “don’t they teach you anything in school these days” would also be possible translations.

It’s also worth emphasizing, for the benefit of those seeing change and decay in all around, that teaching these basic calculating and thinking techniques in public schools was something Wells was proposing as a major reform in education.

From a story in Stuff

The amount of money Kiwis lost to online dating scams has doubled in the past year and now makes up almost two-thirds of all reported online fraud losses.

which then goes on to say

NetSafe operates a website, theorb.org.nz, in partnership with the police, the Consumer Affairs Ministry and other government agencies which lets people report frauds by clicking on an “online reporting button”.

So it’s not a doubling of cybercrime, it’s a doubling of cyberreporting. A bogus poll, in other words.

We then read

The charity claimed in June that cyber-crime cost the country “as much as $625 million” in financial losses once the time and expense in sorting issues, such as removing malware, was included.

If we simultaneously believed the $625 million and believed that the ‘two-thirds’ from online dating scams was meaningful, that would be $400 million per year from online dating scams, which is ludicrous.  So at least one of these figures is bogus.

In fact, they both probably are. The story goes on to say

The journalist is to be commended for at least forcing this admission.  The figures from people selling computer security products are notoriously inflated; there’s a good description of attempts to track down the sources of these numbers from a recent ProPublica article.

It’s hard to visualise big numbers, so it may not be obvious how extreme the $625 million number is.  For example, it’s more than the total profit from NZ beef exports ($2 billion gross, about 25% profit (p22)) , and it’s more than ACC spends on medical treatment each year.

Congratulations to Eric Crampton for his nomination of an absolute shocker of a statistic this week. The printed story completely mangled the information in the press release. It even went further and attributed malicious intent to the researchers.

“67 Maori children died avoidable deaths every year, costing taxpayers $200 million annually.”

The original study says that the social costs of health disparities ranges from $62m-$200m, including measures of the value of statistical lives lost among Maori children. In no way is the larger figure close to a “Cost to the taxpayer” except in the odd sense that costs borne by the parents who cared about those children are included in the value of statistical lives lost and some of those parents may have been taxpayers.

Another case of “Economic Impact” or “Social cost” turning into “cost to the taxpayer” when handled by journalists.

Discussed at length:

http://www.tvhe.co.nz/2012/08/06/journalist-ideological-cant-read/

http://www.offsettingbehaviour.blogspot.co.nz/2012/08/i-hate-economic-impact-numbers.html

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 August 17 2012.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of August 11 – 17 2012 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.

(more…)

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

Team Ratings for Round 23

Here are the team ratings prior to Round 23, along with the ratings at the start of the season. I have created a brief description of the method I use for predicting rugby games. Go to my Department home page to see this.

Performance So Far

So far there have been 160 matches played, 90 of which were correctly predicted, a success rate of 56.25%.

Here are the predictions for last week’s games.

Predictions for Round 23

Here are the predictions for Round 23

The Herald’s headline is “NZ troops more at risk at home than abroad”, but there’s the familiar problem with denominators.

Of more than 3500 injuries recorded between January 2011 and May 2012, 269 were suffered overseas, according to figures released to the Herald under the Official Information Act.

The majority of injuries are in NZ, because that’s where most NZDF staff time is spent.  At the moment, 343 NZDF personnel are on operations and UN missions, and 553 on other overseas deployments.  That’s from a total of 11891 military personnel and 2455 (equivalent full time) civilian staff (annual report, p13).  So, just over 6% of NZDF staff  are deployed overseas, and they get 7.7% of the reported injuries.   They are at more risk overseas, even if you lump together minor sporting injuries with deaths from enemy action.     That’s what you would expect, and it’s what Lt General Rhys Jones is quoted as saying.

Ignoring the denominators misses out the opportunity to comment on the real differences: it’s a bit surprising that being deployed doesn’t increase the injury risk more, but the increase in serious and fatal injuries is probably masked by the noise of miscellaneous exercise-related injury.

One of the problems with lookingfor patterns in Big Data is that there’s a lot of things that look like patterns.  It’s easy to see things that aren’t there.

In a dramatic example, Phil McCarthy feeds a random polygon generator into an automatic face recogniser, and makes random changes to the polygons to improve the recognition score.

(via Ben Goldacre and Prosthetic Knowledge)

As a former Australian, I need to point out that the natural denominator for comparisons between Aus and NZ should include sheep as well as people.

On this metric, Australia has one medal per 4.5 million population, and one gold medal per 50 million population. New Zealand has one medal per  4.4 million population, and one gold medal per 11.8 million population.

Looks like New Zealand is still ahead, even if you include sheep in the population.  On the other hand, Jamaica leaves us both in the dust.