Posts written by Atakohu Middleton (125)

The anti-fluoride Fluoride Action Network has accused the Waikato Times of reversing the results of an online poll that asked whether people supported the council’s move to defer re-fluoridating the city’s water supply until a High Court legal challenge  is decided.

What the Waikato Times did or didn’t do is immaterial. Folks, the paper ran a self-selecting online poll, which makes its results utterly meaningless.

The best poll we have on this is October’s non-binding referendum. It showed that nearly 70% of Hamilton voters favoured water fluoridation.

From the Genetic Literacy Project:

“Up till now, newborn screening has not been done by looking directly at an infant’s genes. Instead researchers check a tiny drop of blood taken from a baby’s heel for certain biochemical markers. These markers indirectly reveal the presence of abnormalities that can be treated effectively early in life.

“That indirect approach could change, depending on the results of four new pilot projects funded by the US National Institutes of Health. The projects are studying whether extending newborn screening to studying the genes themselves makes medical—and ethical—sense.”

Read the whole post here.

Neville Davies, from the Royal Statistical Society Centre for Statistical Education, Plymouth University, UK, is visiting the Department of Statistics at The University of Auckland, the home of statschat.  I asked him to share his first impressions … 

Does New Zealand have one of the most innovative school statistics curriculums in the world? Yes! But how does it compare with the UK?

Well, in the UK for the last 50 years the school statistics curriculum has been hijacked by policymakers and maths teachers who believe the subject is a subset of maths and should be taught as such. And there is research evidence to support this.

This attitude has stifled curriculum development for statistics and helped to make the subject disliked by many school-aged learners. And many schoolteachers dislike teaching it too – it’s a bit of a nuisance that gets in the way of the maths.

But things are much better in New Zealand: here the school curriculum is data-driven throughout and is taught, learned and assessed accordingly. And that’s how it should be.

Everyone should have noticed that we are awash with data: bombarded with the stuff. As more and more people try to make sense of these mountains of data, very often information gleaned from them are at best untrustworthy and often misleading and wrong. It is a matter of common sense that young people should be taught to be confident with what to do about data they see in everyday life, as well as being sceptical about what others claim about them.

The best way to teach the skills necessary is precisely what the New Zealand school curriculum specifies.

By talking to the developers of the curriculum in New Zealand, visiting schools, talking to teachers, attending classes and chatting to students I am discovering how the statistics part of the mathematics and statistics curriculum is being implemented in refreshing and innovative ways. To coin a phrase used in New Zealand school statistics resources,  I am being a ‘data and information detective’  and I will take back to the UK lessons we can learn to try to change what is going in that distant land. It’s a case of grandmother needing to learn new ways to suck statistical eggs!

Watch this space for updates.

Good work by journalist Steve Deane in today’s New Zealand Herald:

A study published by the Lion Foundation which extols the benefits of funding community projects with gambling money is course work produced by a group of Massey commerce students.

… I wonder if the students knew that their coursework, which for various reasons explained in the story can’t be used to draw such conclusions, knew their work was going to be hijacked? Either the Lion Foundation doesn’t know much about statistical rigour, or is grasping at straws and hoping no-one will ask questions.

From today’s New Zealand Herald:

Beauty giant Dove has been forced to take an advertisement for its shampoo off television screens after it was deemed misleading to viewers.

The commercial for Dove Hair Care, which claimed 90 per cent of Kiwi women recommend its products, received a number of complaints from viewers who said it was “clearly misleading”.

 The people “polled” had been sent free samples. Had I been one of them I would have made nice noises too.

Read the full story here.

The below is posted on behalf of Mark Holmes from the Department of Statistics at The University of Auckland. Colleague James Curran read this piece on Wired Science  and challenged him to respond to the following:

Suppose that two drunk statisticians leave a bar (located in the middle of an infinite forest) together.  They stumble around at random and get lost.  Will they ever find each other again?

Mark, helpfully, rose to the bait (thanks, Mark!)  This is what he says:

Assuming 1) that the drunks will live (and stumble around drunk) forever, and that 2) the forest is two dimensional (i.e. there is infinite space to move in both N-S and E-W directions, and the drunks can’t climb infinitely high trees!)  then the answer is yes, they will meet each other again.

Perhaps the best way to explain this is to consider the difference between their locations.  If after n steps the first statistician is at position X_n and the second at position Y_n, then let’s look at D_n=X_n-Y_n.  The two drunks will meet at any time n when X_n=Y_n, which is the same as D_n=(0,0) (the position at time n has two coordinates since we are in two dimensions).

It turns out that D_n itself is essentially a simple random walk, and that the two drunks not only meet again, but they meet infinitely often, because D_n returns to (0,0) infinitely often.  The posh way of saying this is that “simple symmetric random walk in two dimensions is recurrent”.  It is perhaps not surprising that if instead of stumbling around an infinite forest they stumble along an infinite footpath (one dimensional), they will also meet each other infinitely often (“simple symmetric random walk in one dimension is recurrent”).  Note that if the bar is located instead in an infinitely high, wide and long mall they might never meet again (“simple symmetric random walk in three dimensions is not recurrent”).

If the above was good news for the drunks, there is some bad news.  Although they will meet each other again in finite time, the  “average” time it takes them to meet again is infinite.  This is true both in the forest and on the footpath.

If you are interested in the relevant calculations, ask a graduate student in probability (they should also be easy to find on the internet).  If you are satisfied that you understand that, try to solve the following:

 “A physicist, a probabilist and a statistician walk out of a bar…..”

Suppose that we have three independent random walkers instead of two.  The above discussion says that each PAIR of walkers will meet each other infinitely often (in two dimensions).  Will all three meet each other simultaneously?

… so, dear readers, let us have it!  Don’t be shy.

Statistics New Zealand is marking 120 years of women’s suffrage with a nice little infograph (click to enlarge).

The graphics are a recent development, and long may they continue (and that the print media and teachers make the most of them). The last SNZ graphic I saw marked the birth of a certain baby called George, and looked at a range of facts and figures to do with child-rearing in New Zealand.

From the New York Times:

Statistical analysis has swept through baseball over the past decade, becoming part of the fabric of the game and an object of growing fascination to its fans. As players, managers and front office executives embrace the esoteric statistics, teams increasingly want their radio announcers just as fluent in the language of WAR, VORP and B.A.B.I.P.

Say what?

Read the full story here.

The New York Times has reported on a study in which observers sat discreetly in bathrooms and observed whether people “properly” washed their hands (I reckon it would be quite hard to sit discreetly in a bathroom unless you’re in a cubicle). Anyway, the description of the study gave careful attention to the stats: 10.3% of women and over 15 percent of men didn’t wash at all. Of those who did wash, 22.8% did not use soap. And only 5.8% washed for more than 15 seconds.

The lead author said, “Forty-eight million people a year get sick from contaminated food, and the (American) Centre for Communicable Diseases says 50% would not have gotten sick if people had washed their hands properly. Do as your mum said: Wash your hands.”

Surely there’s some basic confusion over percentages here: 50% of those who got sick wouldn’t have if everyone had washed their hands properly, but we have no idea what percentage of those who don’t wash actually get sick.

As a matter of fact, there is no indication that these particular non-handwashers have anything to do at all with the fact that people eat contaminated food. Does it matter what bathroom activity was being carried out? Whether you use toilet paper or your foot to flush? Whether you work in food services? Whether you subsequently wash your hands before eating dinner?

Though mum may have had good advice, this sort of scare-mongering about food-borne illnesses resulting from not washing one’s hands may actually distract us from the real concerns over germs.

• Read the full analysis by Rebecca Goldin, here. She is Director of Research for STATS, an American non-profit, non-partisan service that  helps journalists think quantitatively through providing education, workshops and direct assistance with data analysis.

If you have read media stories recently that say ‘yes’, you’d better read this article from the Genetic Literacy Project …