Posts from August 2013 (54)

Chocolate tastes nice but (sadly) is high in fat, so there’s a lot of potential appeal in news stories that say it’s really terribly healthy. Ideally these stories would come out just before Valentine’s Day, or Christmas, or perhaps Mothers’ Day, but any time of the year will do.

The Herald has a chocolate story, with the lead

Hot chocolate can help older people keep their brains healthy, research has shown.

The research compared blood flow in the brain, and performance on some cognitive function tests. The participants were assigned to drink cocoa with high or low levels of flavonols (aka flavonoids), the chemicals in chocolate that are thought to possibly have beneficial effects.  Based on the headline, you might expect that the researchers saw a difference between the two groups. Sadly, no:

Half the participants were given hot chocolate rich in antioxidant flavanol plant compounds while the other half received low-flavanol cocoa.

Flavanol content made no difference to the results, the researchers found.

That is, participants in both groups improved over the course of the study, regardless of what they drank.  Normally, this would be considered evidence against an effect of chocolate.

For comparison, there’s a more careful story at NPR news, and a less careful one at Forbes. We repeat the  StatsChat position on chocolate “Don’t eat it just for health reasons. If you don’t like it, save it for people who do.”

Some South African readers have asked for Currie Cup predictions and since the methodology should work, I have decided to provide them. Interestingly, the home ground advantage in past games appears to be large, and the predictability of games has varied enormously. Last year’s competition was very hard to predict it seems.

Team Ratings for Round 1

Here are the team ratings prior to Round 1, 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.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Predictions for Round 1

Here are the predictions for Round 1. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 22

Here are the team ratings prior to Round 22, 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 152 matches played, 92 of which were correctly predicted, a success rate of 60.53%.

Here are the predictions for last week’s games.

Predictions for Round 22

Here are the predictions for Round 22. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Stats Chat reader Elizabeth Paton-Simpson emailed us about what would have been a worthy Stat of the Week nomination. It’s from back in June, so isn’t eligible, but I wanted to share it with you:

Elizabeth wrote the following to the Sunday Star Times:

An item in the Sunday Star Times on 2 June was headlined: “Anaesthetics triple risk of dementia for elderly”. Likewise, the opening paragraph proclaimed: “Having a general anaesthetic may triple the risk of dementia in elderly patients, a study suggests.”

Trained to be sceptical of media claims, I read on and found reference only to a 35 percent increase. Checking the purported source revealed that the Sunday Star Times had altered the summary in The Times from “may increase … by a third” to “may triple”. So please tell Grandma she need not be alarmed – it’s just another example of journalistic innumeracy.

The Sunday Star Times responded:

Yes, you’re correct that the Times later corrected their article however we took their wire service copy which originally said “triple”. I’m sorry for any alarm this may have caused! And, of course, you are right that this should have been picked up in our subbing process.

Unfortunately, the statistic remains uncorrected elsewhere, such as The Australian.

Every year, the Discovery Channel has “Shark Week”, which is apparently their top-rated week of the year.  This year they led off with a programme about the extinct shark C. megalodon, which made the great white shark look like a guppy.

Unfortunately, they did a “Does Megalodon still exist?” programme.  The answer is, definitively, “No”, and to get any other answer you’d have to make up some evidence. That didn’t put them off.  Read Christie Wilcox (scientist) and Wil Wheaton (celebrity nerd) for more.

The excuse for putting this on StatsChat is below

I suppose it’s appropriate that they use a bogus poll to try to prove they fooled most of the people who trust them for science communication.

Congratulations to Brendon Blue for his nomination of a the “10,000,000,000,000,000 times likely” statistic in last week’s Stat of the Week competition.

For a discussion on this, please refer to James Curran’s post: “10 quadrillion times more likely to have done it”.

Congratulations Brendon! Please add your nominations to this week’s competition.

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 9 2013.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of August 3 – 9 2013 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!

An excellent long piece about lotteries, from the online magazine Nautilus.  There are many viewpoints presented, including one from the president of the Tennessee lottery corporation

Hargrove has an intuitive understanding of what drives her customers to play the game. She has a preternatural sense of where their psychological buttons are located and how to push them. She responded in a flash to my comment about the logical futility of playing the lottery. “If you made a logical investment choice, you’d play a different game,” she said, leaning forward for emphasis. “It’s not an investment. It’s entertainment. For a very small amount of money you might change your life. For $2 you can spend the day dreaming about what you would do with half a billion dollars—half a billion dollars!”

When  both payoffs and odds that are beyond any conceptual understanding you could do a simple expected-value calculation and label government lotteries as a tax on stupidity, but that framing assumes lottery players are calculating the expected payoff and just getting it wrong. Empirically, it seems to be more complicated than that.

• A good story in the Herald about a survey of health risk behaviour in NZ high-school students. Things are improving, as the story says. There’s even a link to the real research.  Pity about the headline.
• Short free-access piece in the Listener on estimating and understanding risks of death.  There’s a longer cover story in the paid-access or squashed-tree versions, also by Mark Broatch.
• The NZ Science Media Centre has a new edition of its Desktop Guide for Science Reporters. It’s also valuable for people reading science stories — especially those by journalists who haven’t read the guide.