Posts from August 2011 (37)

The Media7 science special that recently screened on TVNZ7 included a section on the best and worst science stories of the last year, some of them really useful contributions and some just woeful. Read more at the-best-and-worst-science-stories-revealed

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 12 2011.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of August 6-12 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.

This week’s competition is now closed, the winner is announced here.

Last week, many newspaper websites (though apparently not any Kiwi ones) reported a study purporting to that users of Internet Explorer had lower IQs than users of other browsers, with IE version 6 users scoring 20 points lower than Firefox users, and more than 40 points lower than users of Opera. The results were supposed to be based on a survey of 100,000 people recruited through ads on websites.  This turns out not to be the case.

What makes the story interesting is how many reasons there were not to believe it. (more…)

David Farrar at Kiwiblog provides some new local examples and discussion of question-wording effects in surveys, including the gender/pay issue and same sex marriage.

“With poll questions there is rarely a clearly “right” or “wrong” question. There can be a dozen different ways to ask a question. The important thing is that the poll results make it very clear the exact question that was asked, and that reporting of the results does the same.”

Read the post »

The Economist has updated its Big Mac Index:

“The Economist’s Big Mac index is a fun guide to whether currencies are at their “correct” level. It is based on the theory of purchasing-power parity (PPP), the notion that in the long run exchange rates should move towards the rate that would equalise the prices of a basket of goods and services around the world.”

At market exchange rates, a burger is 9% more expensive in New Zealand than in America. In other words, the raw Big Mac index suggests that the NZD is 9% overvalued against the US dollar. Adjusting for GDP per person, the NZD is 29% overvalued.

Read more »

From the NZ Herald:

“The survey found almost 65 per cent of women believed they were paid less because of their gender. Just under 43 per cent of men agreed but 47 per cent didn’t.”

Unfortunately the Herald doesn’t tell us what the actual question was. Were people asked whether they, personally, were paid differently because of their gender, or whether women, on average, were paid less because of their gender?   In either case, my sympathies are with Women’s Affairs Minister Hekia Parata, who refused to offer her own answer to the “simplistic” poll question.

There are two statistical problems here. The first is what we mean by “because of their gender”.  After that’s settled, we have the problem of finding data to answer the question.  Inference about cause and effect from non-experimental data will always be hard because of both problems, but that’s what we’re here for.

Usually, when we say that income or health is worse because of some factor, we mean that if you could experimentally change the factor you would change health or income. We say high blood pressure causes strokes, and we mean that if you lower the blood pressure of a bunch of people, fewer of them will get strokes.  This isn’t possible for gender — not only can we not assign gender at random, we can’t even say what it would mean to do that.  Would a female Dan Carter be his sister Sarah, or Irene van Dyk? (more…)

We congratulate our colleagues Maxine Pfannkuch, Matt Regan, Chris Wild and Nick Horton who have been recognised by the American Statistical Association for the best paper in 2011 in the Journal of Statistical Education, Telling Data Stories: Essential Dialogues for Comparative Reasoning.

This is the second major recognition on the world stage in the last year for this group, following on from their read paper before the Royal Statistical Society on World Statistics Day, 20/10/2010.