Posts from October 2011 (39)

Here’s a great collection of 50 statistics blogs which were chosen, amongst other factors, for being nice and accessible to non-statisticians. We also have a list of blogs in our sidebar which has many in common with theirs.

(Of course, we’d love to see Stats Chat included in their list next year! Help us spread the word too.)

Thanks for all the nominations this week, especially all those from Tony Cooper! The winning nomination is: “Drowning deaths soar beyond 2010 total” – there are many such stories in the media where the usual type of variability one would expect to see with counts of events is seen as something unusual:

This is similar to my previous nomination in that it is making headlines out of statistical noise.

90 people have now drowned in New Zealand in 2011 and the drowning drowning toll is predicted to rise to 110 or more by the end of the year.

But an examination of the drowning deaths chart at http://www.watersafety.org.nz/research/ shows that 110 is pretty normal and that 2010 was an exceptional year in being below 100.

Looks like we have a new statistical term “soaring to the mean” to replace “reversion to the mean.”

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 October 14 2011.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of October 8-14 2011 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.

The fine print:

• Judging will be conducted by the blog moderator in liaison with staff at the Department of Statistics, The University of Auckland.
• The judges’ decision will be final.
• The judges can decide not to award a prize if they do not believe a suitable statistic has been posted in the preceeding week.
• Only the first nomination of any individual example of a statistic used in the NZ media will qualify for the competition.
• Employees (other than student employees) of the Statistics department at the University of Auckland are not eligible to win.
• The person posting the winning entry will receive a $20 iTunes voucher.
• The blog moderator will contact the winner via their notified email address and advise the details of the $20 iTunes voucher to that same email address.
• The competition will commence Monday 8 August 2011 and continue until cancellation is notified on the blog.

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

Q:  So what’s with this green tea article at Stuff.co.nz?

A: It’s reporting an experimental study on weight loss using green tea extracts

Q: And did it work?

A: Yes, the treated subjects gained less weight than the untreated ones, by about 4g. (more…)

According to the New York Times, the US Preventive Services Taskforce is about to recommend against routine prostate-cancer screening, based on the results of randomized trials that didn’t show any decrease in overall deaths.   We’ll come back and discuss the report when it actually appears, but this recommendation is going to be profoundly unpopular with certain groups, most dramatically with men who have had prostate cancers detected and removed.

One of the biggest problems in recommending against an existing screening method or treatment is all the complaints from people who think they have personal experience of its effectiveness (most of whom, I can safely predict, won’t actually bother reading the report before denouncing it).  The idea that an individual can know that a treatment works, based just on personal experience, is a very powerful cognitive illusion.  It can’t possibly be true — medical science would be so much simpler if it were — but the perception is unavoidable.   For example, I had mild `walking’ pneumonia a few years ago, and got sicker over a period of weeks, then got treated, and suddenly started to feel better.  It certainly felt as if the treatment worked, but when I later talked to some experts I found out that there is very little reason to believe that antibiotics are helpful for the sort of illness I had, and suddenly starting to feel better is exactly what happens when your body finally gets on top of an infection.  Even so, if you hooked me up to a polygraph you would find I still believe the treatment worked for me.

Cognitive illusions are much like optical illusions: these lines don’t look straight, and you can’t learn to see them as straight, no matter how much optics you study. You just have to decide who you are going to believe — the evidence, or your own lying eyes?

Scientific American’s blog is having a series of posts on how clinical trials for new medicines work (the author describes the series as ‘medicine for muggles’).

Congratulations to one of our department members, Ilze Ziedins, whose research project into improving traffic systems has been funded from the Royal Society of New Zealand’s Marsden Fund.

Her research aims are covered in a story in today’s NZ Herald:

Dr Ziedins said past research has found that when travelling, either by car or through cyberspace, people chose their route without thinking of other people. Statisticians called this behaviour selfish routing, and said it was the cause of long delays and queues.

Road users could already choose to use GPS or webcams to plan their journeys. Backed by the $465,000 grant, Dr Ziedins will investigate whether this more detailed, accurate information could change people’s behaviour and reduce congestion on the road or on the internet.

“The main thing we’re looking at is: ‘Will giving people more information lead to a better distribution of traffic, just in itself? If you more information about the state of the network, will your choices end up making the network work better?,” she said.

The answers to solving these problems were not simply in adding lanes to highways or building more roads.

“In fact, increasing capacity may lead to worse behaviour overall,” said Dr Ziedins.

There was a large amount of fuss made about a week ago (26/09/2011) at various news and hi-tech blog sites about story claiming that “this is the first time a work of Shakespeare has actually been randomly reproduced.” On the surface of it, this seemed utterly implausible.

For those of you not familiar with the “Infinite Monkeys theorem”, it essentially states that “an infinite number of monkeys randomly bashing away on typewriters/keyboards for an infinite amount of time will almost surely recreate the entire works of Shakespeare.” You can read more about it here on Wikipedia.

I took a look at the author’s own site and found the description of his experiment quite confusing with poorly defined objectives. It seemed to me that he was just randomly generating character sequences and if he found a matching word within the relevant Shakespeare text, then he counted it as completed. This is not what I understood as the Infinite Monkeys theorem because there is no requirement that the words be generated in the correct order. What was even more puzzling was his choice of 9-characters at a time.

I asked my esteemed colleague Professor Thomas Lumley for his thoughts on the matter. He had this to say:

“In order to get this to work in reasonable time, it sounds as though he is working with nine-character random strings and keeping each string if it matches some nine-character substring of Shakespeare. This means that he is guaranteed to finish in about 27^9 samples (if he uses just letters and spaces).

If he used one-character sequences it would be over a lot faster, and with 20-character sequences it would take a very, very long time.

I assume the 9-character limit was so that the Bloom filter fits in memory easily.”

Thomas also discovered another blogger making almost identical points.

It seems that the Bard is safe from monkeys for some time to come.

Ratings at the Start of RWC 2011

Here are the team ratings at the start of RWC 2011.

Of interest in this table is that the eight top-ranked teams are the ones which have progressed to the quarter finals.

Current Team Ratings

Here are the team ratings as of October 05, 2011

The most notable change here is the improvement of Wales taking it above England. Ireland has also improved, but France is down. Of the lesser teams, Samoa, Tonga and Georgia have improved, Fiji has declined and Namibia has deservedly sunk further into the mire.

Performance So Far

So far there have been 40 matches played, 36 of which were correctly predicted, a success rate of 90%.
Here are the predictions for the games so far.

Predictions for the Quarter Finals

Here are the predictions for the quarter final games

Most interesting here is the very narrow gap between South Africa and Australia. That game could clearly go either way.

Source File: hwriterPredictions.R

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