Posts from August 2012 (64)

A nice page by Christopher Healey, at North Carolina State University.  Among other things, it includes demonstrations of change blindness  and of preattentive perception:

For many years vision researchers have been investigating how the human visual system analyses images. An important initial result was the discovery of a limited set of visual properties that are detected very rapidly and accurately by the low-level visual system. These properties were initially called preattentive, since their detection seemed to precede focused attention. We now know that attention plays a critical role in what we see, even at this early stage of vision. The term preattentive continues to be used, however, since it conveys an intuitive notion of the speed and ease with which these properties are identified.

Typically, tasks that can be performed on large multi-element displays in less than 200 to 250 milliseconds (msec) are considered preattentive. Eye movements take at least 200 msec to initiate, and random locations of the elements in the display ensure that attention cannot be prefocused on any particular location, yet viewers report that these tasks can be completed with very little effort. This suggests that certain information in the display is processed in parallel by the low-level visual system.

The limits of preattentive perception are why you can’t usefully represent more than four or five groups of points in a scatterplot, no matter how creative you get with colours and symbols.

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 31 2012.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of August 25 – 31 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.

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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!

Stuff has a story pointing out that conspiracy theories go together:

If you think smoking doesn’t cause lung cancer, HIV doesn’t cause Aids or Nasa faked the Moon landing, you are also more likely to support free market economics and be sceptical about climate change.

An apparently stronger version of this was demonstrated in a study published in January this year,

A New York Times story about buying and selling favorable online reviews

Many of the 300 reviews he bought through GettingBookReviews were highly favorable, although it’s impossible to say whether this was because the reviewers genuinely liked the books, or because of their well-developed tendency toward approval, or some combination of the two.

[Update: XKCD]

XKCD (come on, you know XKCD): I can’t help but admire the audacity of the marketer who came up with the phrase “contains a clinically studied ingredient”

headsup (journalism blog): It’s more likely that the [Detroit Free Press] doesn’t understand that you’re supposed to do a little basic arithmetic before you talk about public opinion.

Andrew Gelman: graphs showing uncertainty in a fitted curve.

journalism.org.nz: a proposal for NZ public interest journalism funded by the public

BBC: Gathering evidence for the effects of exercise on depression is harder than you might expect.

Stuff is reporting on a software system called Volpara for improving breast-cancer screening, from Wellington company Matakina (and 3News had a similar story).  The software is designed to give more reliable and objective estimates of breast density, with less variation due to different equipment or different radiologists.  This should be helpful in screening younger women, either to improve detection of tumours or to reduce false positives, and the software seems to have been quite successful commercially.

Medical progress is pretty incremental: even the best ideas and techniques tend to have relatively small impact on health, so while it’s good to see NZ medical contributions being recognised, it’s also useful to put them in context. (more…)

The Herald says

One in three New Zealanders have been harmed by their own alcohol drinking, a survey shows.

The survey, published in the New Zealand Medical Journal, found 33.8 per cent of current drinkers reported they had been adversely affected in the past year.

This is actually true: there is such a survey, it is published in the NZMJ, and it’s a real survey (the response rate isn’t all one could wish, but it’s not out of line with other major health surveys).  The story goes on to say that the harm was reported more often by men.

The interesting point is that the current issue of NZMJ has two articles about frequency of harm from drinking.  The other one says, also based on real survey data,

The prevalence of self-reported harm from others’ drinking was higher than harm from own drinking (18% vs 12% in the past year) and was higher in women and young people.

And this second survey isn’t pro-alcohol in the slightest — for example, it quotes the proportion of criminal offenders who had been drinking as if it was the proportion of crimes resulting from alcohol.  This is a huge overestimate, precisely because there is too much drinking in NZ: the people who are drunk and arrested in the major cities tend to be just as drunk about three times a week on average (based on Massey Uni. research that we’ve mentioned before).

The timing of these articles is perhaps not a coincidence, but in fact there’s pretty wide consensus about the harms from drinking: the real disagreement is about the costs of various sorts of regulation.

Team Ratings for Round 25

Here are the team ratings prior to Round 25, 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 176 matches played, 103 of which were correctly predicted, a success rate of 58.52%.

Here are the predictions for last week’s games.

Predictions for Round 25

Here are the predictions for Round 25

At Simply Statistics, a set of stat/data related startups.

One that looks interesting for teaching and for data journalism purposes is Statwing, which is building a web-based pointy-clicky data analysis system, aiming to have good graphics and good text descriptions of the results.  This is the sort of project where the details will matter a lot — poking around at their demo there were a few things I was slightly unhappy about, but nothing devastatingly bad, so there is potential.