Posts from October 2015 (50)

Team Ratings for Round 10

The basic method is described on my Department home page.

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

Performance So Far

So far there have been 36 matches played, 26 of which were correctly predicted, a success rate of 72.2%.
Here are the predictions for last week’s games.

Predictions for Round 10

Here are the predictions for Round 10. 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.

There are new (provisional) suicide figures out for the year to June, and the Herald has a story (and has embedded the summary report).

The problem with news stories on this topic is that the important statistics haven’t changed.  Suicide rates have been pretty much constant over the 9 years of data shown. It’s still true that New Zealand has a high suicide rate, that it’s much higher for men than women, and that it’s much higher for Māori than non-Māori, and lowest for Asians.

There were slightly more suicides this year than in recent years, almost the same per-capita rate as in 2011/12.  Most of the increase was in men, but it’s still not any sort of clear sign of a trend.  The Herald story leads with the changes, as news has to, but the real story is that we still haven’t managed to change anything.

It’s time for Forest & Bird’s Bird of the Year competition. As with any bogus poll, we won’t learn what the true popularity of the various NZ birds actually is.

As long as it’s clear that bogus polls are being used for entertainment and advertising, not to collect information, there isn’t a statistical problem with them.

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 9 2015.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of October 3 – 9 2015 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!

Team Ratings at 04 October

The basic method is described on my Department home page.

Here are the team ratings prior to 04 October along with the ratings at the start of the Rugby World Cup.

Performance So Far

So far there have been 26 matches played, 21 of which were correctly predicted, a success rate of 80.8%.
Here are the predictions for previous games.

Predictions for 04 October to 07 October

The prediction is my estimated expected points difference with a positive margin being a win to the first-named team, and a negative margin a win to the second-named team.

From the Independent, which used to be the sort of paper that knew better:

With a 100 per cent record up to this point – they predicted England would beat Fiji but lose to Wales – it seems that the meerkats might have some genuine psychic abilities. 

Even if they do, that doesn’t explain why they care about rugby, or how they know which flags painted on pebbles correspond to which group of large men.

Yes, I get that it’s not supposed to be true. Simon Rice probably doesn’t believe the meerkats are psychic. He probably doesn’t expect his readers to believe the meerkats are psychic (and if they did, they would have been terribly disappointed). In the old days of paper newspapers though, you could distinguish stories that were supposed to be true from the ones that weren’t supposed to be true by a lot of positioning and formatting cues. 

With the move from paper to digital, the presentation of news stories that are supposed to be true is getting more similar to the presentation of news stories that aren’t supposed to be true.  That’s especially an issue for health science news: even when the reporter knows which stories are news and which are nutribollocks, it can be hard for the reader to tell.

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From the Daily Mail (via the Herald) “Need a boost? Try orange juice, not coffee“,  reports on a study comparing high-pulp orange juice not to coffee but to orange-flavoured water. The story says

After the real juice they did better on tests of speed and attention and still felt very alert six hours later, the European Journal of Nutrition reports.

The research paper is here (open access, no link).  There were ten tests of speed and attention and mood, each done at two times after the orange juice.   If you chose the most-impressive of the twenty comparisons and pretended it was the only one that mattered, you’d get some reasonable evidence that orange juice gave a slight improvement over fake orange juice. If you take into account the changes in all the measurements it looks much less convincing.  A combined analysis of all the measurements “approached significance,” as people say when they don’t get the hoped-for results.

And “felt very alert six hours later“? That’s a 6% difference between fake and real orange juice on a “how alert do you feel?” scale, plus or minus about 6.4%.

It’s a pity that Pepsi, who sponsored the study and sell the juice, didn’t make it a bit bigger so that any real effects would be convincing and chance fundings would be more clearly too small to worry about.

Under the headline “Studies show food preferences are written in genes,” the Herald has an interesting story by CSIRO scientist Nicholas Archer about genetic variation in taste and smell receptors (and largely not about food preferences). The same story was at The Conversation, under the headline “Blame it on mum and dad: how genes influence what we eat.”

The text makes much more reasonable claims about food preference. It says

Food preferences vary and are shaped by three interacting factors: the environment (your health, diet and cultural influences); prior experience; and genes, which alter your sensory perception of foods.

and later

Genetics has also been linked to whole foods, such as coriander preference, coffee liking and many others. But genes have only a small influence on preference for these foods due to their sensory complexity and also the contribution of your environment and prior experiences.

It’s only the headlines that are over the top, but that’s a consistent problem with genetics stories.

When you see a genetics headline, the first thing to think about is whether the trait it talks about has changed over the past century or so. Human genetics hasn’t had time to.

We can look at changes over recent time to show the enormous non-genetic influences on food choice. The biggest ones are due to wealth, but there are actual changes in preferences as well.

For example, raw fish would have been an unusual food preference for Aucklanders of European descent forty years ago. It’s not that raw fish was unavailable back then; that was how it came from the shop. It’s just that people didn’t eat it raw, because ick. Now, raw fish is an absolutely routine form of fast food. That’s not because of a change in genetics, it’s because of cultural change spreading from the US.  As another example, many European-ancestry people like spicier food than their parents or grandparents did, not because of a change in genetics, but because of a change in exposure to spices early in life.  You can easily think of more.

“Mum and dad” do have a big influence on what we eat, but most of it happens well after conception.

• Algorithm audit and cheating (from NYT): there is a class of software that successfully goes through tight regulatory auditing — it’s not voting machines, it’s gambling machines

• If you use a round-number price on eBay you will sell faster, for less.

• Book recommendation: How Not To Be Wrong: The Power of Mathematical Thinking, by Jordan Ellenberg. The only thing wrong with this book is that he’s misspelled “Statistical” in the subtitle.

• Book recommendation: Eureka: Discovering Your Inner Scientist, by Chad Orzel. A good guide to how science actually works; useful for dispelling the myth that scientists are mutant geniuses who do qualitatively different stuff from normal humans.